Getting there: From Walnut Creek go east on Ygnacio Valley Rd. and turn right on Walnut Avenue. Follow signs into Mt. Diablo State Park and continue up the road to the top of the mountain. Just before the final ascent to the summit, turn into the large parking lot on the right. Walk back across the road to the beginning of the trail.

Difficulty: Easy; the three-quarter-mile loop is nearly level.

Setting: The trail takes you around the mountain just below the summit with many varied exposures and sweeping vistas. Plant communities include oak woodland, chaparral, and rock scree.

Special plants: Rayless arnica (Arnica discoidea), western waterleaf (Hydrophyllum occidentale), canyon larkspur (Delphinium nudicaule), Brewer's rock cress (Arabis breweri), a white-flowered form of bitter root(Lewisia rediviva), a pale form of sickle-leaved onion (Allium falcifolium), red rock penstemon (Keckiella corymbosa), winecup clarkia (Clarkia purpurea), California psoralea (Pediomelum californicum), chaparral harebell (Campanula exigua), tincture flower (Collinsia tinctoria), clustered broomrape (Orobanche fasciculata), and many more. The best time to visit is from May to early June.

Canyon larkspur pictured.