The Sierra Azul (“Blue Range”) is an open space preserve in the South Bay region of Santa Clara County. At 18,400 acres, it’s the largest preserve in the district. The area is dominated by Mt. Umunhum, a 3,486 foot peak capped by the “blue cube” the former Almaden Air Force Station. This station was part of the early warning radar network of the 1950’s. Now closed and abandoned the entire are around Umunhum is unfortunately closed to the public. Due to the closure the next best peak is Umunhum’s sister peak, Mt. El Sombroso.
The summit of Mt. El Sombroso at 2,999 feet is a 12.3 mile round trip hike. Primarily fire road, it meanders through deep forest cover for much of the hike. The last few miles of the hike you’ll earn your summit – the gradient turns steep, covered in loose shale, and most of it is spent in direct sun. Hot and tired you’re rewarded with sweeping views of San Jose and the entire South Bay basin. If you have a clear day you’ll be able to spot Mt. Hamilton across the valley.