Located high up at an altitude of a little more than 5,000 mts is the mysterious Roopkund Lake. This glacial lake in Uttarakhand has a strange claim to fame. When the frozen lake melts, hundreds of skeletons can be seen floating in the water. From scientific to religious, there are a number of theories behind this mystery. It, however, hasn't affected the beauty of this place and tourism still thrives here. It is a popular trekking destination in Garhwal district of Uttarakhand state, and is also the site of Nanda Devi Raj Jat, a religious festival celebrated every twelve years.