Enthusiasts of Mayan archaeology will find some of the best hieroglyphic carvings in the whole of the Mayan world along with well-restored structures, including palaces, temple pyramids, and a ball court.
The Hieroglyphic Stairway [1] alone is worth the price of admission, not to mention the chance to see the buried section of temple pyramids from tunnels (Rosalila and Los Jaguares [2]) originally used by archaeologists excavating the ruins.
Links:
[1] http://www.moon.com/destinations/guatemala/el-oriente-and-izabal/copan-archaeological-site/copan/hieroglyphic-stairway
[2] http://www.moon.com/destinations/guatemala/el-oriente-and-izabal/copan-archaeological-site/copan/tuneles-rosalila-y-los-jaguares