Lake Calavera Preserve

On our list of the best activities in San Diego.

Mount Calavera at the heart of this preserve is a volcanic plug roughly 15 million years old, mined for basalt gravel for about 25 years before conservation took over, and the lake below it sits behind a dam built during World War II. A loop of about 3.4 miles climbs from Oak Riparian Park through oak woodland and marsh boardwalks before a steep, rocky push to the summit, where Palomar Mountain and the snow line on San Jacinto show up on a clear day. Dogs are welcome throughout, and the preserve shelters six threatened or endangered species, including the California gnatcatcher, with stone labyrinths and a sealed former mine cave along its trail network.