Cuevas del Drach are caves located next to city of Porto Cristo in Mallorca. It contains one of the largest underground lakes in the world. When we were there, they were showing documentary about Jules Verne and the Journey to the center of the Earth on the cave walls. Together with the music and echoes, it was really cool experience. Once you reach the underground lake (Lake Martel), you can see musicians on the boat playing classical music.