Indiana Jones style travel - What to see???

I'm planning a trip to South America and would love to explore the ancient historical cities/ruins but am looking for suggestions.

Already on the list are a number of Mayan ruins (Central America really), Machu Pichu and other Incan ruins, but I'm sure there's a lot more interesting and less well known places.

I'd love any thoughts from the community!

Ciudad Perdida in Colombia. Requires several days of jungle trekking to reach.

Though not nearly as impressive as Machu Pichu, Northern Peru is littered with hundreds, if not thousands of ancient ruins. Many unknown except to serious archaeology buffs. So they're very untouristed. I know that Peru is even trying to steer traverlers northward to these very sights to ease the tourism pressure off of places like Machu Pichu and Cuzco, which are being "loved to death." When I get down to south america this year, I may visit some of these in Northern Peru. It sounds like you're going to be in Central America as well, Southern Mexico and in El Peten, Guatemala is also littered with many lesser Mayan sites. Several years ago, when I stayed in the Lacandon village of Lacanja, in the Lacandon Jungle (go figure!), my guide showed me some mayan statues that had been unearthed naturally when a dead tree had fallen over and revealed some old Mayan handiwork buried underneath. He told me that a prestigious university was scheduled to do some field work in the area. But the place had Mayan ruins everywhere. Most buried.

-Ciudad Perdida, Colombia
-Bonampak and Yaxchilan, Mexico (Chiapas)
-El Mirador and El Zotz, Guatemala