Indian Ladder Trail Guided Walk at Thacher Park. 10 a.m. See underground streams, look for fossils and step inside the crevice cave along the trail. The trail is moderately rugged with stair climbing and a couple of steep slopes. Wear sturdy shoes and meet at the Indian Ladder Trailhead behind the Visitor Center. Walk lasts about 1.5 hours. Call 872-0800 to register.