Irish Hills Natural Reserve sits just outside San Luis Obispo and packs way more trail variety than you’d expect from its footprint. Despite being only 720 acres, the reserve has over 8 miles of marked trails with multiple loop options, so you won’t feel like you’re retracing the same path repeatedly. The terrain shifts between single-track sections and old double-track routes left over from the area’s mining days, which actually helps break up the ride nicely and connects different sections of the reserve.

The landscape itself is genuinely interesting—rocky serpentine soil supports a mix of chaparral, oak woodlands, grasslands, and riparian areas depending on where you venture. You’ll climb to around 1,100 feet if you do a full loop, which makes for a solid workout without being overwhelming. Most outings run between 5 to 7 miles round trip and take 2 to 4 hours depending on pace and how much exploring you do.

Dogs are welcome here as long as they’re leashed, and the trail conditions suit most fitness levels, though “moderate to strenuous” is the honest rating. The variety keeps things engaging—you’re not just grinding uphill for hours.

Getting to the main Prefumo Canyon Trailhead is straightforward: take Los Osos Valley Road north from Highway 101 toward Los Osos, then turn left onto Prefumo Canyon Road. The trailhead is on the left about a mile up, just after crossing a bridge. If you prefer starting from the Madonna Road Trailhead instead, take Los Osos Valley Road north again, but this time turn left on Madonna Road and follow it to the end. You’ll find street parking and then walk up the dirt road to reach the actual trailhead. Both access points give you flexibility depending on where you want to spend your time in the reserve.