La Gruta is a small bat cave in the centre of Isla Colón, a few kilometres from Bocas Town along the road toward Bluff Beach. The cave is easy to miss — it appears as a dark opening in a low limestone cliff beside the road — but inside it opens into chambers filled with thousands of bats hanging from the ceiling. A clear, shallow stream runs through the base of the cave, and it is possible to wade through the cave from one entrance to another.
The walk-through takes about 15–20 minutes if you follow the stream channel. Bring shoes you don't mind getting wet and a torch (the cave is very dark despite its short length). The cave is managed informally; there's a small donation box at the entrance. It makes a good stop on a bicycle circuit of Isla Colón, combined with visits to Bluff Beach and Starfish Beach on the same day.