 The Canyon to Lake section of the Grand Loop Road follows the eastern side of the valley near the river.The geothermal features that are scattered around the valley are not as impressive as those of the large geyser basins, but in many case they were the first to be discovered and described by the early explorers.They include Mud Volcano, Mud Geyser, Sulphur Caldron, and Black Dragon Caldron at the southern end of the valley and Sulphur Spring in the Crater Hills group further north and west of the river.