Geologists date the volcanic rock formations to the Permian period, roughly 280 million years ago, when tectonic upheaval fractured the Mediterranean basin. By the eighteenth century, Genoese mariners had charted these waters as treacherous, marking Mezu Mare — the largest island at sixty-five hectares — with warning beacons long before France erected its stone lighthouse in 1870.
Today the archipelago functions as a protected marine reserve, its rocky shorelines hosting rare Audouin's gulls and Mediterranean monk seals that return each spring to the submerged caves beneath the western cliffs. The lighthouse on Mezu Mare remains operational, its automated beam rotating at intervals through the night, though the keeper's quarters now stand empty. Botanists catalogue fifteen endemic plant species adapted to salt spray and thin volcanic soil, including dwarf holm oak and wild mastic shrubs that cling to crevices inaccessible to goats.
Most sanguinaires islands boat trip departures launch from Ajaccio's Tino Rossi harbour between April and October, when swells drop below one metre and visibility extends past Cap de Feno. Operators favor rigid inflatables for the thirty-minute crossing, their shallow drafts permitting close approaches to sea caves where limestone meets granite in geological collision. The archipelago cruise route typically circles Mezu Mare counterclockwise, allowing passengers to observe the layered stratigraphy of the northern cliffs before landing at the lighthouse dock.
Archaeologists recovered Roman amphorae fragments from underwater surveys conducted in 1998, evidence of ancient trade routes threading through these channels when the islands served as waypoints between Sardinia and the Provençal coast. During World War II, German forces installed observation posts atop the highest promontory, concrete bunkers still visible among the maquis scrub. The French Navy decommissioned the military installations in 1962, returning the islands to their prior isolation broken only by seasonal boat traffic and the lighthouse's metronomic flash.
2 hr 30 min
