Carved by an ancient underground river, 1200m-long Bacho Kiro Cave was inhabited way back in the Palaeolithic era. In 1937 it became Bulgaria's first tourist cave, and today it's often twinned with a visit to nearby Dryanovo Monastery. Entry is by semi-guided tour, which involves a little historic preamble (usually in Bulgarian only), after which you can take a short or long (25 minutes or one hour) walking route around the cave.
From the bridge near the monastery's car park, a 400m-long path and cobbled stone stairs lead through the forest to the cave.