The caves at Pinnacles are talus caves, formed when steep, narrow canyons were filled with boulders, leaving passages between the larger rocks. Bear Gulch Cave on the east side of the park and Balconies Cave on the west side are seasonally open to visitors. Trails lead to and through both caves. These caves house breeding colonies for Townsend's big-eared bat and are closed during pupping season. The caves may be flooded at times of high water. The National Park Service maintains a webpage showing the status of the caves.