Strandzha Nature Park — Bulgaria's largest protected area — surrounds Primorsko on three sides. The park covers oak and hornbeam forests descending to the Black Sea coast, with rivers running through deep valleys and the Turkish border cutting through the forest to the south. It is one of the few remaining areas of primary deciduous forest in Europe, and the birdlife is exceptional: over 250 species have been recorded, including Egyptian vulture, lesser spotted eagle, and several owl species.
For walkers, marked trails lead from several villages into the forest, ranging from easy riverside walks to longer routes through the hills. The village of Brashlyan, inland from Primorsko, has a collection of well-preserved Bulgarian National Revival houses and makes a good base for forest walking. The rivers in the park — particularly the Ropotamo — can be explored by boat from the northern park boundaries.