I actually had a close up on how the caryatids are placed at the Erechteion. Notice though that these are, just as a great number of other ancient pieces in the field, are modern copies while the originals are to be found in museums. Yet, they clearly show you how they were used. Another place where you find a lot of copies is Pompeii. If you ever go there, notice how many tourists there are, taking shots of the famous (copy) faun (in Casa del Fauno). It's actually attracting thieves too from time to time, and the authorities have to replace it with regular intervals.