West of Danville, two long ridges frame a narrow valley along Bollinger Creek.
The park
Las Trampas covers 5,342 acres in Alameda and Contra Costa counties, according to Wikipedia. Las Trampas Ridge runs along the east and Rocky Ridge along the west, with a horse stable and parking in the valley between them. Some trails have as much as 900 feet of elevation change, and the park has been called "the tough guy of the East Bay Regional Park District."
The name
The park district says Las Trampas is Spanish for "the traps" or "the snares." Citing Erwin G. Gudde's California Place Names, it says traps were once set in the chaparral to catch elk. Wildlife includes raccoons, foxes, bobcats and deer, and golden eagles are occasionally seen. The district leases some grassland for cattle grazing.
Visiting
The main entrance is the Bollinger Staging Area at 18012 Bollinger Canyon Road, reached from Crow Canyon Road. Hours are 8 a.m. to 7 p.m. through Nov. 1, then 8 a.m. to 5:30 p.m. from Nov. 2. The district warns that the park's water supply is unreliable, so visitors should carry plenty of water for themselves, their dogs and their horses.