Google Street View has sent people on bicycles around 30 major archaeological sites in Mexico, including Chichen Itza, Palenque, Monte Alban, Teotihuacan, Tulum, Cobá, and more. You can go right up to (but not up) the pyramids. For me, seeing the tourists and the souvenir vendors is part of the fun. Daniel Hernandez at the LA Times has some more good links.
Ancient observatories from space Satellite images of Angkor Wat, Chichen Itza, Chaco Canyon, Stonehenge, Teotihuacan, and others. The observers, observed. High res images available.