Spring Lake Natural Area is the wild backside of the San Marcos springs

Spring Lake is the pool the San Marcos River pours out of, fed by the Edwards Aquifer welling up through the Balcones faults. The famous side is the water: the glass-bottom boats, the diving Aquamaids of the old Aquarena Springs days. Less known is the high ground above it: Spring Lake Natural Area, 252 acres of undeveloped city parkland with more than six miles of trail climbing from meadow up into oak-juniper hillside.

It sits in the Sink Creek watershed, and about half the property lies over the Edwards Aquifer Recharge Zone, the porous limestone where rainwater drops straight into the rock that feeds the springs below. Walk it and you're literally on top of the plumbing that keeps the river running through droughts that dry up everything around it.

The trails are free and open to hikers and mountain bikers, with the trailhead off Spring Lake Drive on the north edge of San Marcos. Pair a morning here with the boat tour down at the Meadows Center and you've seen both halves of the same spring system — the water and the watershed that recharges it.