The smattering of islands off the coast of Kotka are former military outposts, some of which are now open to the public. Several boat trips depart from Sapokanlahti. From June to August, the MS Klippan (adult/child €8/4) runs hourly to Varissaari, where there are the remains of an 18th-century naval fortress. In July and August, the MS Jaana (adult/child €20/10) makes the 45-minute journey to the island of Rankki, returning 2½ hours later.

Accessible by free public ferry (from May to September), Kirkonmaa still contains a battery and military housing, set amid beautiful nature. All three islands have a summer cafe and other recreational facilities.