Chichén Itzá, Mexico — At the spring and fall equinoxes, the setting sun casts serpent-like shadows along the northern stairs of El Castillo, or “the castle.” Built more than a thousand years ago by ...

Archaeologists working in a tunnel beneath Teotihuacan's Pyramid of the Sun have unearthed two caches of artifacts that may have been meant to consecrate the massive building's construction around a.d ...