Santa Rosa has a state park within its city limits.
The rocks
Trione-Annadel sits at the northern edge of Sonoma Valley, next to Spring Lake Regional Park, according to Wikipedia. Its rock formations run through its history: a volcanic origin, Native American use of obsidian, cobblestone mining in the early 1900s, and the outcrops hikers enjoy today. Wappo and Pomo people lived on these lands. Some biologists consider the park's northern oak woodland among the best undisturbed examples left. The park was established in 1971. It was one of the 70 state parks slated to close in 2012, and Sonoma County ran it temporarily to keep it open.
Fires
The 2017 Nuns Fire burned the southern portion of the park, and the 2020 Glass Fire burned its northern edge. Wikipedia says Lake Ilsanjo, the park's largest body of water, has black bass and bluegill.
Visiting
State Parks says the park is open 8 a.m. to sunset every day, with no overnight use. Vehicle day use is $7. Dogs are allowed only in developed areas such as Channel Drive, not on trails. The entrance is at 6201 Channel Drive, off Montgomery Drive. State Parks recommends a hike around Lake Ilsanjo for wildflowers from early spring to early summer.