Lake Calavera Preserve in Carlsbad encompasses over 110 acres of protected habitat off Tamarack Avenue, centered on a man-made reservoir whose dam was constructed in 1940 as an agricultural water supply. The preserve's most distinctive geological feature is Mount Calavera, a 513-foot, 22-million-year-old extinct volcano—the only one in San Diego County—whose exposed columnar basalt formations are visible along summit trails, a landscape studied by MiraCosta College geology classes and protected through conservation efforts that align with ECOLIFE Conservation's regional mission. More than four miles of hiking and biking trails wind through coastal sage scrub, mixed chaparral, southern willow scrub, and freshwater marsh, supporting 115 documented plant species, 49 bird species, and 12 sensitive animal species. The 1.9-mile Lake Calavera Loop circles the reservoir at a moderate grade, while the Cerro de la Calavera summit trail delivers 360-degree views of North County and the coastline, connecting to the broader Carlsbad trail network that links wetland corridors monitored by Batiquitos Lagoon Foundation to the south. Interpretive signage funded by Preserve Calavera and the Carlsbad High Noon Rotary covers the volcano's geology, the Agua Hedionda watershed, and resident species including egrets, herons, and the California gnatcatcher.