I have always been fascinated by Mayan ruins, and Copán is of course right up there. But one of the things that especially sets it apart for me is its museum, which includes a polychromatic reconstruction of the Rosalila Temple, the main religious sanctuary in the late 6th century CE. Offhand I can't recall any other Mayan site which has something like this, giving visitors a window into what structures actually looked like during the era in which they were in use.

(talk2winik)