The Junípero Serra Museum, in Presidio Park, can be seen from Interstate 8 as you drive through San Diego's Mission Valley. It was here that a Spanish Franciscan missionary, Father Junípero Serra, and a group of soldiers established Alta California’s first mission and presidio (fort) in 1769.
This is considered to be the birthplace of the state of California.
The actual fort has since crumbled away, but there is a museum in it's place. There are large swaths of grassy areas where you can have a picnic and view the San Diego River from this high vantage point.
There's an extensive exhibit featuring the Kumeyaay peoples who first lived here as well as other native tribes in the state of California.