Yagodina is the Rodopi Mountains' longest cave at 8.5km, and its many abysses and labyrinthine tunnels also make it one of Bulgaria’s deepest grottoes. The 45-minute tours leave on the hour and highlight curtain-like rock formations and knotty stalagmites, resembling towers of profiteroles. From October to May, at least six visitors are required for the tour; in summer, its 10. The cave is a winding 20km drive south of Devin; you'll need private transport. Trigrad village is 2.3km south of the road from the cave entrance.
Temperatures in the cave are a consistently chilly 6°C so dress warmly.