Burgas is a 40-minute bus ride away and worth half a day for its long sea garden, the lake-shore wetlands, and a more workaday city contrast to Sozopol's heritage. Boat trips from Sozopol harbour run in summer to St. Ivan Island, the monastery ruins, and the smaller St. Cyricus Island just offshore. The salt lakes around Burgas — Atanasovsko, Pomorie, Mandra — are good for birdwatching, with pelicans, flamingoes, and migrating waders in spring and autumn.
Inland, the Strandzha mountains are about an hour's drive south, a quiet and underdeveloped corner of Bulgaria with old Thracian sanctuaries and a handful of preserved villages. The Greek border is two and a half hours from Sozopol if you want a long day trip into the Évros delta.