10 Epic Construction Projects That Took Centuries to Complete

These ten cathedrals and basilicas around Europe (and beyond) were built over many generations, reflecting changes in style, politics, and technology. From the Sagrada Família in Barcelona to the Basilica of San Petronio in Bologna, each project faced delays due to wars, funding shortages, and shifts in power. Some took more than six centuries to finish; others remain unfinished to this day. Their histories show how architecture evolves over time and adapts to challenges.

These buildings stand as monuments to human perseverance, creativity, and faith. Below is a look at each site’s timeline and key milestones in its long construction.

Related: 10 Significant Biblical Archaeology Discoveries

10 Sagrada Família (Barcelona, Spain)–144 Years and Counting

Construction of the Sagrada Família began in 1882 under architect Francisco de Paula del Villar, but it was Antoni Gaudí who transformed the project into his magnum opus in 1883. Gaudí devoted the last fifteen years of his life entirely to the basilica, imbuing its façades and towers with rich Christian symbolism drawn from nature and geometry. The design marries Neo-Gothic and Art Nouveau forms, with twisting columns and hyperboloid vaults that evoke forests, bones, and honeycombs.

Each of the eighteen towers represents an important Biblical figure, and Gaudí’s master plan included elaborate sculptural programs on the Nativity, Passion, and Glory façades. Funding has always relied on private donations and ticket sales, a model that both preserved artistic freedom and created funding uncertainty. From the earliest days, craftsmen—stonemasons, ironworkers, and sculptors—have collaborated closely, continuing Gaudí’s practice of blending art, engineering, and spirituality.

Progress paused during the Spanish Civil War when anarchists burned Gaudí’s workshop and destroyed many original plans and models. Reconstruction of his workshop drawings from photographs and fragments became a Herculean task for later architects intent on staying true to his vision. Advances in computer-aided design since the 1980s have accelerated construction, enabling the translation of Gaudí’s complex geometries into buildable stone and concrete elements.

Modern engineering solutions—such as pre-cast sections—have made possible the simultaneous construction of multiple towers. Despite controversies over stylistic deviations, the basilica’s growth continues under the guidance of the Sagrada Família Foundation. As of 2025, completion is slated for 2026, the centenary of Gaudí’s death, when the Glory Façade and final tower devoted to Jesus Christ are expected to be finished.^[1]

9 Cologne Cathedral (Cologne, Germany)–632 Years

The foundation stone for Cologne Cathedral was laid in 1248, the same year construction began on Beauvais Cathedral in northern France, marking the pinnacle of High Gothic ambition. Master builder Gerhard von Rile oversaw the initial phases, aiming to create a pilgrimage church to house the relics of the Three Magi. The design called for soaring twin spires, ribbed vaults, and a vast interior accommodating thousands of worshippers.

Work continued steadily until 1473, when financial shortfalls and shifting political priorities forced a halt. For over three centuries, the half-finished nave stood as a striking ruin against Cologne’s skyline, symbolic of both aspiration and interruption. During this hiatus, the western towers rose only to a third of their planned height, while the eastern choir and transepts showcased intricate stained glass and sculpture.

A revival of Gothic aesthetics in the 19th century, fueled by burgeoning German nationalism, reignited interest in completing the cathedral. Detailed studies of medieval sketches and stone fragments allowed architects like Ernst Friedrich Zwirner and later Richard Voigtel to resume work in 1842. By 1880, the spires and façade had reached their intended 515-foot (157-meter) zenith, making it the world’s tallest building until 1884.

The completion was celebrated as a triumph of cultural heritage, uniting craftsmanship across centuries. Over the next decades, the cathedral also became a focal point for music, with its renowned choir and organ drawing visitors worldwide. Today, it remains both an active place of worship and one of Germany’s most visited landmarks, testament to perseverance across six and a half centuries.^[2]

8 Milan Cathedral (Milan, Italy)–Nearly 600 Years

Ground was broken on the Milan Cathedral, or Duomo di Milano, in 1386 under Archbishop Antonio da Saluzzo to replace the older churches on the site with an epic Gothic monument. Italian, French, and German master masons contributed to its design, which features an extraordinary forest of pinnacles—over 130 spires crowned by 3,400 statues. The decision to use white Candoglia marble required intricate logistics, including construction of canals and barges to transport the stone.

Work on the main structure—comprising five naves and a monumental choir—continued through the 15th century, but progress waxed and waned with the fortunes of Milan’s ruling Visconti and Sforza families. Rich ornamentation extended well into the Renaissance, as sculptors added altars, reliefs, and elaborate ironwork grilles. By the early 17th century, the façade remained largely incomplete, marked by a skeletal outline awaiting its crowning elements.

Political turmoil, French and Spanish rule, and Napoleonic appropriation shifted funding and priorities throughout the 18th and 19th centuries. Napoleon himself ordered the façade’s completion in a neoclassical style, though subsequent restorations reinstated Gothic motifs. The final decorative copper statue of the Madonnina was hoisted onto the highest spire in 1774, symbolizing Marian protection over the city. Yet finishing touches—such as sculptural groups, stained glass, and pinnacles—continued sporadically into the 20th century.

Post-war restorations and modern conservation projects have sought to stabilize the marble and clean centuries of soot from the exterior. Though structurally complete, the Duomo remains a living edifice, with craftsmen still engaged in preservation and occasional additions. Its gleaming marble façade, visible across the Piazza del Duomo, epitomizes Milan’s layered history of devotion, power, and artistic excellence.^[3]

7 Westminster Abbey (London, England)–Over 500 Years

Westminster Abbey’s Gothic incarnation began in 1245 when King Henry III laid the cornerstone for a grand new church dedicated to St. Peter. Architects Henry of Reyns and later Henry of Sauvage introduced Early English Gothic features—pointed arches, clustered columns, and intricate tracery—designed to reflect Rome’s St. Peter’s while asserting English ecclesiastical identity. The nave and choir were largely completed by 1269, but the western towers remained unfinished when work halted in the 14th century.

Notable additions during this era included the Lady Chapel founded by Edward I, whose geometric vaulting and figural bosses foreshadowed the Perpendicular style. Over the 15th century, successive monarchs and patrons funded chapels, tombs, and screens, weaving the Abbey ever more tightly into royal and national narratives. Its role as coronation church for English—and later British—monarchs, beginning with Edward II in 1308, cemented its status as a symbol of continuity and sovereignty.

The Perpendicular Gothic phase culminated in the completion of the nave’s clerestory and vaulting under Henry VII in the early 16th century, resulting in the magnificent Henry VII’s Chapel featuring fan vaults and alabaster tombs. The Dissolution of the Monasteries under Henry VIII threatened its survival, but its royal associations spared it from destruction, even as many monastic buildings were demolished.

Subsequent centuries saw Georgian and Victorian restorations led by architects like Sir George Gilbert Scott, who repaired medieval fabric and added new seating, lighting, and decorative elements. The iconic twin western towers designed by Nicholas Hawksmoor were finally completed in 1745, giving the Abbey its familiar silhouette.

Today, Westminster Abbey functions as both a living church—hosting daily worship and royal services—and a museum preserving centuries of art, sculpture, and manuscript treasures. Recent efforts have focused on conservation against pollution and subsidence, ensuring this centuries-old structure endures as a centerpiece of British cultural and spiritual life.^[4]

6 St. Vitus Cathedral (Prague, Czech Republic)–585 Years

The foundation stone for St. Vitus Cathedral was laid in 1344 by Emperor Charles IV, who intended it as the coronation church of Bohemian kings and a repository for the Crown Jewels. Master builder Matthias of Arras directed the initial Gothic design, emphasizing a cruciform plan and soaring choir. After Arras died in 1352, his assistant Peter Parler introduced innovations such as net vaulting and irregular window tracery, giving the cathedral a uniquely Czech interpretation of Gothic forms.

Parler’s workshop produced an array of sculptural details—bosses, gargoyles, and figural capitals—that enrich the interior and exterior façades. Work continued through the 15th century on chapels and portals, but the Hussite Wars (1419–1434) and later religious conflicts halted progress. By the mid-16th century, the choir and transept were largely complete, but the nave remained roofless and exposed to the elements for generations.

It was not until the 19th-century revival of medieval culture and Czech nationalism that construction resumed in earnest. Under architects Josef Kranner and later Josef Mocker, restoration of surviving medieval walls preceded completion of the nave and western towers in neo-Gothic style. The final phase, overseen by Kamil Hilbert, culminated in 1929—coinciding with the city’s millennium celebration—when the massive bronze doors and stained glass windows were installed.

The cathedral’s mix of original Gothic vaults and 20th-century stained glass by artists like Alfons Mucha exemplify its layered history. Ongoing conservation addresses issues such as stone weathering, metal corrosion, and structural monitoring to preserve its intricate vaulting and sculptural program. Today, St. Vitus stands not only as the spiritual heart of Prague Castle but also as a symbol of Czech cultural resilience throughout centuries of upheaval.^[5]

5 Ulm Minster (Ulm, Germany)–513 Years

Construction of Ulm Minster commenced in 1377 to replace an earlier Romanesque church, with the ambitious goal of creating the world’s tallest church tower. Master mason Heinrich Parler initiated the flow of fine-grained sandstone blocks onto a cruciform foundation, erecting the choir and transepts in a High Gothic idiom. The eastern sections, including the choir stalls and stained glass, were largely completed by the mid-15th century, displaying rich iconography and alabaster statuary.

However, funding shortfalls—exacerbated by the 16th-century Protestant Reformation and the Thirty Years’ War—halted all work by 1543, leaving the eastern nave roofless. During this intermission, the empty shell served as a market and even as council meeting space, its skeletal silhouette a reminder of unfulfilled aspirations. Meanwhile, the western towers remained mere stumps against the Swabian sky, awaiting the day they would pierce the heavens.

A resurgence of civic pride in the 19th century, linked to Romantic nationalism, revived interest in completing Ulm Minster. Beginning in 1844, craftsmen used original plans and medieval fragments to rebuild the nave, erect the western towers, and finish the lofty spire. By 1890, the spire reached 530 feet (161.5 meters), claiming the title of the world’s tallest church tower—a record it still holds. The interior’s soaring nave and slender columns create the impression of an endless upward pull, underscoring the medieval quest for divine proximity.

Modern conservation teams now grapple with preserving the sandstone façade from acid rain and freeze-thaw cycles, employing gentle cleaning and microcrystalline treatments. Ulm Minster remains a testament to communal perseverance across half a millennium, merging medieval devotion with 19th-century ambition.^[6]

4 Rouen Cathedral (Rouen, France)–Over 400 Years

The origins of Rouen Cathedral date back to the 4th century, but the current Gothic structure began to rise in the early 12th century under Archbishop Rotrou II. Its three-level elevation—arcade, triforium, and clerestory—set a precedent for Rayonnant Gothic design across northern France. The west façade, rebuilt in the 13th century, presents a profusion of niches filled with statues, while the transept arms were heightened to accommodate new rose windows.

Construction proceeded through the 16th century, adding flamboyant Gothic elements such as ornate pinnacles and intricate tracery on the south transept. Wars with England and periodic urban fires slowed progress, and the Reformation introduced further interruptions as funding shifted to military needs. Scholars estimate that active building spanned roughly 118 years, but piecemeal additions and restorations have extended work well into the modern era.

In the 19th century, Eugène Viollet-le-Duc led restoration efforts aimed at reversing centuries of neglect and previous “repairs” that had obscured the original Gothic details. He reconstructed flying buttresses, replaced lost statuary, and reimagined the spire—culminating in the 1876 addition of a cast-iron flèche that soars 495 feet (151 meters) above the city. This modern spire, though stylistically distinct, honors the medieval spirit of verticality and lightness.

Ongoing conservation addresses stone erosion from Seine River pollution, while specialists use laser scanning to monitor structural movements in the nave and transepts. Today, Rouen Cathedral is celebrated for its photogenic façades—famously painted by Claude Monet—and remains a focal point for tourism, scholarship, and parish life. Its layered construction history embodies the resilience of Gothic architecture through war, revolution, and industrialization.^[7]

3 Florence Cathedral (Florence, Italy)–140 Years

The Duomo of Florence, officially Santa Maria del Fiore, was commissioned in 1296 to signify the city’s wealth and piety, replacing the earlier Santa Reparata. Arnolfo di Cambio designed the initial Gothic plan with a massive cruciform nave and elegant pointed arches. By 1418, the cupola over the crossing remained an engineering conundrum—its span too wide for traditional wooden centering.

Filippo Brunelleschi solved the problem in 1420 with an audacious double-shell dome, built without scaffolding by employing herringbone brickwork and custom hoisting machines. This feat marked the dawn of Renaissance engineering, inspiring countless architects across Europe. The dome’s lantern, designed by Brunelleschi and completed in 1461, crowns the structure and is topped by a golden orb and cross. Beneath the dome, the marble-clad façade by Emilio De Fabris, completed in 1887, harmonizes white, green, and red marble in a neo-Gothic revival style.^[8]

2 Cathedral of St. John the Divine (New York City, USA)–Over 130 Years

Conceived in 1889 by the Episcopal Diocese of New York, the Cathedral of St. John the Divine aimed to be the largest cathedral in Christendom. Architect George Heins began work in Romanesque-Byzantine style in 1892, but the death of his partner Christopher Grant LaFarge in 1919 prompted a shift to Gothic Revival under Ralph Adams Cram. The choir and apse were completed by 1941, featuring lancet windows and flying buttresses imported from English cathedrals for study.

Two world wars, the Great Depression, and fiscal crises repeatedly stalled construction, leaving large portions of the nave unfurnished and roofless for decades. The unfinished nave earned the cathedral the moniker “St. John the Unfinished,” but also made it a symbol of artistic experimentation, hosting avant-garde installations and community events. The towering western façade, with its massive twin towers and carved tympanum, remains a work in progress, punctuated by scaffolding and occasional public art projects.

Despite its unfinished state, St. John the Divine serves as a cultural hub, hosting concerts, art exhibitions, and interfaith services that reflect New York’s diversity. A substantial restoration effort from the 1980s to the early 2000s sealed the roof, repaired stonework, and installed modern lighting to showcase stained glass windows by Charles Connick and Lee Lawrie’s sculptural façade.

Fundraising efforts continue for the completion of signature elements such as the central dome and permanent altar furnishings. The cathedral’s treasury now features Byzantine icons, medieval manuscripts, and modern art commissions, underscoring its dual role as both a museum and a house of worship.

Community outreach programs—feeding the homeless, supporting immigrant communities, and promoting environmental stewardship—anchor its mission in social action. As it approaches 140 years since groundbreaking, St. John the Divine stands as a testament to ambition, adaptability, and the unfinished work of faith.^[9]

1 Basilica of San Petronio (Bologna, Italy)–Over 600 Years

Construction of San Petronio began in 1390 on the orders of Pope Boniface IX, intended to rival St. Peter’s in Rome as a symbol of Bolognese civic pride. Architect Antonio di Vincenzo designed a vast Gothic nave capable of holding 28,000 worshippers, with lateral chapels funded by noble families. The imposing brick façade was never completed according to the original marble and bronze scheme; instead, the lower portion remains in plain brick, contrasting sharply with the ornate interior.

Work progressed steadily until the 16th century when funding dried up and civic politics intervened—members of the Bentivoglio family clashed with papal authorities over control of the project. During this hiatus, masterpieces such as Jacopo della Quercia’s marble portal and Giovanni da Modena’s fresco of the Last Judgment were installed, enriching the basilica’s artistic heritage.

Attempts to finish the façade in the 17th and 18th centuries failed amid shifting tastes toward Baroque and Neoclassical styles, which contrasted with the building’s original Gothic language. In the 20th century, restoration campaigns focused on preserving the basilica’s frescoes, such as Giovanni da Modena’s 1410 cycle depicting a vivid hellscape, and the Chapel of the Magi’s exquisite polychrome marble work.

Modern engineers have installed seismic monitors to protect the centuries-old masonry from earthquakes, while art conservators use advanced imaging to assess pigment degradation in frescoes. Today, San Petronio remains incomplete externally but stands fully functional as one of Europe’s largest brick churches. Its vast interior hosts concerts of sacred music and public events, underlining its enduring role at the heart of Bologna’s religious and civic life.^[10]