Pasadena's Church of the Angels is a good place to start. It's the oldest church in Pasadena (built in 1889), rich in history and still active today. It appears in films and TV from time to time.
My friend Bob Goldstein used to be a docent at Pasadena Heritage and probably still would be, had he not moved away from southern California. He loved that volunteer position and relished giving tours of Pasadena's historical neighborhoods. Bob took his post card collection with him, but he's shared some good scans with me. He sent tour information, too—
There'll also be more pictures of Church of the Angels in the next few days, thanks to Kelly. She showed me around her beloved church and read to me about its history. A beautiful old building is a treasure, an old church a quiet mystery. When you and your friend have that to yourselves, it's a special kind of blessing.