Caves like Jeita are made by water. Rainwater slowly trickles through cracks in the rock for thousands and thousands of years. Tiny bits of stone dissolve in the water and then build up again, drop by drop, into amazing shapes. The pointy ones hanging from the ceiling are called stalactites; the ones growing up from the floor are called stalagmites.
Inside the upper cave, one stalactite has been measured at 8.2 metres long - that is one of the longest in the world. Walking under it feels like standing under a giant stone icicle. Soft lights make the rock walls glow pink, blue and gold.
The lower cave is the surprise. You climb into a little electric boat that floats silently along an underground river. The water is icy cold and so clear that you can see the rocks at the bottom. There is no sound except the drip-drip of water from above.
The cave is so important to Lebanon that it was once one of the top 14 finalists in a global vote to choose the 'New 7 Wonders of Nature'. Today it is one of the country's most-loved places to visit, especially for school trips.