Castle Lake fills a plunge-pool at the base of a 300-ft tall cataract at the opposite (east) end of the Great Cataract Group from Dry Falls, above the east end of Deep Lake.
A set of steel ladders put in place during the construction of the Columbia Basin Irrigation Project allow for a safe descent into the basin. In the basin are great views of giant potholes, the flood-sheared face of Castle Rock, as well idyllic Deep Lake.
The Castle Lake Basin lies along the east end of the Great Cataract Group. At the base of the cataract is lovely blue-green Castle Lake plunge pool nestled into the rock bench below.
Castle Lake lies within a single recessional cataract canyon eroded down to a flood-swept, pothole-studded rock bench that stands 100 feet above Deep Lake. This is the same rock bench of Grande Ronde Basalt where dozens of potholes occur at the opposite (western) end of Deep Lake.
Castle Rock itself is an isolated butte along the west side of the Castle Lake basin. It is a faceted butte escarpment nearly sheared off by monstrous flood forces moving across the cataract.