One of the most interesting pieces of evidence I think from Ancient Astronaut theory is the inscription on King Pakal's tomb. Here is a picture, as well as a link to an .svg render of the markings.

From Wikipedia:
Pakal's tomb has been the subject of ancient astronaut hypotheses since its appearance in Erich von Däniken's 1968 best seller, Chariots of the Gods?. Von Däniken reproduced a drawing of the sarcophagus lid, incorrectly labeling it as being from "Copán" and comparing Pacal's pose to that of Project Mercury astronauts in the 1960s. Von Däniken interprets drawings underneath him as rockets, and offers it as possible evidence of an extraterrestrial influence on the ancient Maya.

In the center of that frame is a man sitting, bending forward. He has a mask on his nose, he uses his two hands to manipulate some controls, and the heel of his left foot is on a kind of pedal with different adjustments. The rear portion is separated from him; he is sitting on a complicated chair, and outside of this whole frame, you see a little flame like an exhaust.

Could this be evidence of ancient technology? Could Pakal himself have been an extraterrestrial, meddling in the affairs of the ancient Mayans? When you look at these inscriptions, what do you see?