in the Middle East; it sits at above sea level and has a height difference of . Geologically, the caves provide a tunnel or escape route for the underground river, which is the principal source of Nahr al-Kalb. The Jeita grotto is the longest explored cave in Lebanon. After many years of exploration, speleologists have penetrated about from the entry point of the lower grotto to the far end of the underground river and about of the upper galleries. Upper cave The Jeita upper cave has an overall length of of which only are accessible to visitors via a specially conceived walkway; access to the remainder of the cave was restricted to prevent ecological damage which may occur due to the flocking tourists. The upper cave contains a great concentration of a variety of crystallized formations such as stalactites, stalagmites, columns, mushrooms, ponds, curtains and draperies. The upper gallery is famous for its formations, lit by an effective lighting system. It is entered through a long concrete tunnel. The part accessible by visitors has three huge chambers. The first is called the White Chamber, the second Red Chamber. White dripstones are pure calcite without defilement, the red color is given by iron oxide (rust) in small amounts. In Lebanon, iron oxide has a red color instead of the brown beige color which is common in northern countries. The reason is a different chemical reaction caused by the high temperature which produces a different kind of iron oxide. The White Chamber is medium-sized, but has the most impressive formations of the cave. The Red Chamber is up to high, and to wide. The third chamber is the biggest of all three chambers and has a height of more than . The longest stalactite in the world is located in Jeita's White Chamber; it measures long. Lower cave The lower gallery which has an overall length of is located below the upper gallery. It is traversed by a smooth underwater river and a lake (the "Dark Lake"). The river is broken up by several small cataracts and rapids. The lower cave's "Thompson's Cavern", is a massive hall with impressive speleothems such as the Eagle Obelisk stalagmite. Other halls in the lower gallery include the Pantheon, Grand Chaos and Shangri-la. Visitors are transported in the lower gallery by electric boats for a distance of . In winter the lower level is closed, when