The Blue Cave opens beneath a limestone overhang on the Luštica Peninsula, ten nautical miles southwest of Kotor. Its entrance is submerged at high tide; only boats with shallow draft and helmsmen familiar with the Adriatic's tidal calendar can thread the approach. Once inside, visitors find a domed chamber forty metres wide, lit entirely by sunlight refracted through seven metres of seawater. The effect is visible only between late morning and early afternoon, when the sun's angle sends rays upward through the cave mouth. The result is a sapphire glow that clings to the limestone ceiling and dyes the water an electric cyan. Locals call it Plava Špilja — the name appears on Venetian nautical charts from the sixteenth century, though the cave itself predates those records by several millennia. Blue Cave tour from Kotor itineraries pair the grotto with a circuit of the inner bay's historic landmarks. Most speedboat departures include a swim stop inside the cave, a passage through the Mamula submarine tunnel — a concrete-lined channel carved by Yugoslav naval engineers during the Cold War — and a mooring at Our Lady of the Rocks, the man-made islet that rises from a reef two hundred metres offshore from Perast. The artificial island was constructed over four centuries by mariners who sank captured enemy vessels and loose stone atop the reef after every safe return. By 1630, the platform was stable enough to support a baroque church and a votive museum. The route also passes the fifteenth-century fortifications at Perast, the Renaissance palazzi along the waterfront in Risan, and the narrow strait that separates Kotor's fjord from the open Adriatic. The bay's coastal topology — a drowned river valley flanked by the Orjen and Lovćen massifs — creates microclimates that shift within a few kilometres. Morning fog banks settle over the inner narrows near Verige, while the outer bay remains clear. Afternoon thermals off the limestone slopes generate choppy conditions that subside by evening. Speedboat operators time their blue cave tours to align with both the tidal window and the sun's refraction angle, departing Kotor harbour between 09:00 and 10:30 to reach the cave during peak luminosity. The route covers approximately thirty-five kilometres round trip, with a typical duration of three to four hours depending on swim stops and weather holds. Entrance to the cave itself is free; the museum on Our Lady of the Rocks charges a two-euro conservation fee, collected on arrival.