The Caves of Drach, or “Dragon caves” are four great caves that are located in the island of Majorca. They are situated near Porto Cristo. They were first mentioned in a letter 1338. The caves extend to a depth of 25 m, reaching 2.4 km in length. The four caves, called Black Cave, White Cave, Cave of Luis Salvador, and Cave of the French, are connected to each other. The caves have formed by water being forced through the entrance from the Mediterranean Sea, and some researchers think the formation may date back to Miocene era. There is an underground lake situated in the caves called Martel Lake, which is about 115 m in length and 30 m in width, and its depth varies between four and twelve meters.