Las Trampas Regional Wilderness, Regional park in Alameda and Contra Costa counties, California

Las Trampas Regional Wilderness is a 5,342-acre East Bay Regional Park District park in Alameda and Contra Costa counties, nearest Danville. Two long ridges, Las Trampas Ridge on the east and Rocky Ridge on the west, flank a narrow valley along Bollinger Creek, which holds a horse stable and visitor parking. Rocky Ridge reaches 2,024 feet; trails can involve up to 900 feet of elevation change.

The area received its name from Spanish settlers who used the word Trampas to describe the traditional hunting methods in this region. The landscape was shaped by human use over centuries before being designated as a protected wilderness area.

Las Trampas is Spanish for "the traps" or "the snares." The park encloses the Eugene O'Neill National Historic Site on three sides; hikers can reach it via trails from Las Trampas or by a single-lane road from Danville.

Visitors should bring plenty of water since drinking facilities are limited and not always available year-round. Sturdy hiking boots are important for handling the varied elevations and different trail conditions throughout the park.

The exposed rock formations in the park contain layers of marine fossils that reveal traces of ancient shorelines. These geological layers show that this region was once submerged beneath ocean water.