Fodor's Expert Review Postojnska Jama

This is one of the largest networks of caves in the world, with 23 km (14 miles) of underground passageways. A miniature train takes you through the first 7 km (4½ miles) to reveal a succession of well-lighted rock formations. This strange underground world is home to the snake-like "human fish," on view in an aquarium in the Great Hall. Eyeless and colorless because of countless millennia of life in total darkness, these amphibians can live for up to 60 years. Temperatures average 8°C (46°F) year-round, so bring a sweater, even in summer. Tours leave every hour on the hour from May through October, six times a day in April, and three times a day from November to March.