Saint John is the largest of the five islands in the Bulgarian territorial waters of the Black Sea with an area of 0.66 km2. It is 910 meters away from the northernmost point of the peninsula Stolets (old Sozopol). Its highest point rises 33 m above sea level.

On St. Ivan was built a sonar marine lighthouse that beeps and - along with the lighthouse on Cape Emine - shows the way of the vessels to the Bourgas Bay.

The island was a holy place for the ancient Thracians who made their sanctuary here in the 7th century BC. Then a large temple complex was erected on the southern coast of the island, whose center is the 13.2 m high bronze statue of the god Apollo Healer, made by sculptor Kalamis.

The island is visited by boats and small ship from the port of Sozopol. There are two harbors on the island, from which go marked tourist paths leading to the archaeological monument - the monastery "St. John the Baptist ". Access is strictly forbidden by a ministerial decree in the period April-July (until July 30) when the gulls are nesting.