Pruitt's Castle is a striking natural rock formation located at mile 24. 5 on the Lower Owyhee River near Chalk Basin, featuring distinctive rhyolite cliffs with holes and white spikes banded with brown and red lava streaks that resemble a medieval fortress.

Several good campsites with hiking opportunities are available in the area, making it a popular scenic stop for rafters and kayakers during the spring float season (March-June).

The formation is easily accessible from the river and offers excellent photo opportunities and side hike options for multi-day boating trips.