[jcwade]

The Griffith Observatory is great but usually packed. If you go, get there really early or expect a long hike up the hill from the street parking. It also cost a ton per hour so check the signs.
The LA Zoo is a good place as well as the Gene Autry Museum.
They are also in Griffith Park across the street from each other with free parking.
The zoo has great exhibits but if it's hot the animals just lay around. The Autry is all cowboy stuff, including a great collection of firearms of the old west. It is billed as western heritage, not western history so there are exhibits about western movies as well.
Up in the same area is Universal Studios.
Also, the Getty Center in Westwood has great views of the city as well as great art.
The Getty Villa in Malibu is designed after a Roman Villa buried by Vesuvius and has a fantastic collection of ancient art. Both Gettys are free, except for parking but you need to make an appointment, which can be done on their app.