This 150-million-year-old cavern was discovered accidentally in 1985. It's 57m deep and filled with multicoloured stalactites and other rock formations that have whimsical names such as the Pipe Organ, Cacti and Jellyfish.
The cave is illuminated with floodlights, and connected via a series of platforms and staircases – be prepared for some climbing. A steady temperature of 18°C is maintained, and humidity is a moist 95%. Guided tours are mandatory and run every 30 minutes.
The cave is signposted as ‘Olympi Cave’.