Featuring limestone passageways, ancient marine fossils, stalactites, and unique geological formations along the Bonnechere River. Guided tours take visitors through one of Ontario's most remarkable natural attractions.

Best Features:
- 500-million-year-old limestone cave system
- Ancient fossils, stalactites, and unique rock formations
- Guided underground tours with scenic river viewpoints

Why it's popular:
Visitors are drawn to the rare opportunity to explore an ancient cave network, learn about Ontario's geological history, view fossils from a prehistoric tropical sea, and experience complete darkness deep underground during guided tours.