Pyramid Lake is located near Dixon, Nevada & is part of the Pyramid Lake Indian Reservation.  The Truckee River flows into the lake - the lake itself is part of the ancient Lake Lahontan w/ lakeshore levels apparent on the hillsides from the Pleistocene era.  The lake is known for its tufas & hot springs/geysers, though public access is not allowed.  On the east side is a small tufa formation w/ a pyramidal shape, giving the lake its name.