The Witcher wiki now has a light themed alternative for the wiki skin. To check it out, go to Special:Preferences, then choose the "Appearance" tab and click on the radio button next to "Hydra".
There are several altars in The Witcher and The Witcher 2: Assassins of Kings. Some of them are more like locations than objects, others serve as containers and still others are merely décor. Here is a list of the location-type altars: