South of the spreading suburbs of San Marcos, a scruffy ridgeline scrapes the southern sky. Topographic maps note the obscure names of its various high points: Cerro de las Posas, Double Peak, Franks Peak, and Mount Whitney (not that Whitney, but still the highest of the group). Double Peak lies within a future 200-acre City of San Marcos regional/interpretive park atop the ridge. Already there's public access to Double Peak by way of old fire roads and newly cut trails. Travel is permitted by foot, horse, and mountain bike.