Hi Brad,
Like David, I've visited Stonehenge in England. There's also a village close by called Avebury that is almost completely encircled by stones. I've been to Machu Picchu in Peru (five times) and was a part of an Earthwatch expedition in (LONG ago) 1982. Dr. Ray White (now deceased) and Dr. David Dearborn were investigating the alignments of the Torreon (round room) and the Intihuatana stone (and other places). Like Stonehenge, when I was there in 1982, you could touch the stones there, but sometime in the late 80's or early 90's (by 1994, anyway), the Torreon, the Intihuatana stone and a few other areas were roped off. I've uploaded a picture showing the Torreon (the roundish structure near the middle of the image).
In the Yucutan of Mexico, I visited Chichen Itza, Tulum, Xel Ha, and Coba. In Guatemala, I visited a site in downtown Guatemala City.