Urban Exploring in or near Riverside

I'm going back to Riverside from San Francisco and was wondering if anyone knew of any abandoned buildings or areas that not many people go to? I love exploring since there is an abundance of these locations around me and I like to see these places almost frozen in time. I've looked around Riverside and have only found graffiti waterfalls, the portal, and a bunker in Fontana. Does anyone know any other locations or at least clues on how to find them?

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