Saint Ivan is the biggest of the five islands in the Bulgarian territorial waters of the Black Sea with an area of 0.66 km2. It is 910 m away from the most northerly point of Stolets peninsula (old Sozopol). Its highest point rises 33 m above sea level.
The island shelters a sonar lighthouse (42°26′19″ north latitude, 27°41′26″ east longitude) that gives audible signals and together with the lighthouse on Cape Emine shows the way to the Burgas Bay.
The island was a sacred place for ancient Thracians who made a sanctuary here as far back as VII century B.C. At that time, they erected a big temple complex on the south coast with its center in the 13.2-meter high bronze statue of god Apollo Physician – a work of the Greek sculptor Calamis.