Location: Monte Alban mountain, In the Oaxaca Valley.

Description - Believed to have been built around 600 BC. A huge complex of ceremonial buildings on top of Monte Alban mountain. It has some of the most oddly shaped structures of the ancient world. No two sides or angles of the building are equal. Slabs on the outside are inscribed with symbols and hieroglyphs that are still not fully deciphered. (12)

References:

12). The atlas of mysterious places. Guild publishing. 1987.