Fortaleza de Sagres sits on a flat, wind-scoured limestone promontory at the south-western corner of Europe. The earliest documented fortifications were raised here under the patronage of Henry the Navigator in the 1440s, and from this clifftop Portugal's captains were dispatched down the African coast in the decades that opened the Atlantic. The school-of-navigation legend that Henry founded a formal academy here is contested by modern historians — what is certain is that the prince held court at Sagres and that the place was the operational nerve of Portuguese deep-sea exploration in the mid-15th century.
The fortress was sacked in 1587 by Sir Francis Drake during the Anglo-Spanish War, and was further damaged by the 1755 Lisbon earthquake. What stands today is therefore largely a Vauban-style 18th-century rebuilding, with the inland wall — the long sawtooth bulwark that visitors cross on entering — dating to the reconstruction. The 16th-century Igreja de Nossa Senhora da Graça survives inside the perimeter, modest in scale but the oldest standing building on the promontory.
In 1921 archaeologists uncovered an enormous stone-paved circle, 43 metres across, set into the ground near the church. Its purpose remains disputed: it has been variously interpreted as a 15th-century wind rose used for navigational instruction, a mariners' compass, or a sundial. The structure is now the fortress's most photographed feature and the centrepiece of every tour. Fishermen still cast for sea bream from the basalt cliffs along the southern perimeter — a tradition that pre-dates Henry's arrival.
Today the site is operated by Museus e Monumentos de Portugal (MMP) as a national monument. The visit is largely outdoor: a roughly one-kilometre clifftop circuit, with permanent exhibitions in the gatehouse and the former governor's quarters. Cabo de São Vicente, six kilometres west, is the actual south-western tip of mainland Europe — but Sagres is the cape its lighthouse was built to defend. On a clear afternoon both lighthouses (Sagres and São Vicente) are visible from the wind rose.