The actual source of the Yamuna is located at the very difficult-to-reach Saptarishi Kund. You must have a guide to go there. It is believed that seven great Rishis—Kasyapa, Atri, Bhadravaj, Visvamitra, Gautama, Jamadagni, and Vasistha— performed austerities for millions of years here in Satya-yuga.
It takes 16 hours to go up and back down. You have to deal with the high altitude, climbing up hills and over rock, ice, snow, and water. The kund is about a half km in diameter, and its water is dark blue with slushy snow. Very few people come here, as it is a difficult place to reach.