Can't afford to forget this one, it will gain importance: The World's Largest Pyramid Is Hidden Within a Hill in Mexico

[TlalocW]

1. I've been there twice

In high school and college. Passageways have been excavated through the pyramids (plural). Tribes in the area tended to ritually destroy things every 52 years then rebuild on the ruins. So you can walk through them and see how the layers differed. Funnily enough, the group I was with both times had the same guide. He laughed when I told him. Down the hill one one side is an ampitheater that's been partially excavated. It was thought that theatrical works and important speeches were given there because the design of it amplifies your voice.