Since I’ve stumbled across a number of ancient chapels and churches in unexpected places over the years, it shouldn’t have come as such a shocker one summer in the south of France, next to the Mediterranean, near a narrow spit of land to the west of Palavas-les-Flots (a resort town just south of Montpellier). But there it was, mere steps away from where I was learning to kitesurf: an ancient fortress-like cathedral next to the beach.

The Saint-Pierre de Maguelone cathedral can come as a bit of a surprise to surfers, tourists and beachgoers in their birthday suits (it’s also a naturist area) zipping around nearby. The most striking thing, and what “also makes it an incredibly picturesque destination, is the cathedral’s isolation, floating on that little finger of land between vineyards, lagoon and sea,” says Elizabeth Emery, a professor of French language and culture at Montclair State University. Because “cathedrals are, by definition, seats of bishops,” she adds, you expect “to find them in large urban centers, not on islands.”

The cathedral’s long history involves the likes of the Visigoths, Romans, Saracens and Franks. Religious structures on this tiny island, wedged in between the Étang de l’Arnel lagoon and the Mediterranean, date back to the 1st century. The Germanic Visigoths moved in and founded a diocese here after the Roman Empire crumbled. The Franks destroyed the original cathedral — which had been converted to a mosque — in the 8th century during their conflict with the Saracens.

Gerardo Boto Varela, professor of medieval architecture and art history at the University of Girona, Spain, points out the “fascinating and singular” elements of this fortified church’s design, with “stairs integrated into the wall, choirs on high, lateral apses that do not project to the outside and very strong towers on the sides of the building.” In other words, Maguelone was the Fort Knox of cathedrals in its day. Maguelone, which is a “Romanesque church [built] on the walls of the Visigothic church,” Varela explains, regained its ecclesiastical glory when it became the regional bishopric from the 6th to 16th century — although it was essentially abandoned for centuries after, once the diocese was relocated to Montpellier in the 1500s.

These days, apart from lush surroundings and stunning ocean views, visitors to Maguelone — now an active archaeological excavation site maintained by the Compagnons de Maguelone — can enjoy the reconditioned grounds, cool cathedral (literally, which is great on a hot summer’s day) and island in large part to the efforts of archaeologist and historian Frédéric Fabrège, who took over the property in 1852. Fabrège restored the cathedral and the Saint-Blaise chapel, planted trees across the (once) barren island and brought the abandoned diocese back to life.

Along with maintaining the tranquil surroundings and small vineyard, preserving the rich architectural history and organizing the Maguelone Early Music Festival held every June (and other concerts throughout the year), the Compagnons de Maguelone also runs Établissement et Service d’Aide par le Travail (ESAT). The organization helps adults with disabilities find work in a natural setting through viticulture and wine production, as well as hawk their goods (wine and fish) at a special shop on the island. Admission to the cathedral and grounds is free, with an audio guide costing around 4 euros (about $4.60).

After a stroll along the Mediterranean, and perhaps a dip in the water (sans clothing or not), the Saint-Pierre de Maguelone cathedral offers the curious a rewarding reprieve from the sun, sea and sand, with a deep glimpse into the region’s storied history.