Although alot of Charmed's sets were computer generated some were not. Although the underworld all looks the same, Charmed specially built lots of different sets for the show and mixed and matched dressings to get the maximum effect. Some of the underworld sets are noticeable that they have been re-used with signature details like flooring ect. However, Charmed was a dab hand with a pot of paint. The Bay Mirror office actually moonlights as the police station. There is one set corridor that became a psychiatric center, morgue, hospital among other things. The Charmed Manor itself is not exactly what it seems to be and isnt in San Francisco, the interior is on Paramount lot and the exterior is located in L.A., infact Charmed never even set foot in San Francisco and used stock footage for the shots of the city we see.