El Infiernito is a Muisca archaeoastronomical site about 8 kilometres from Villa de Leyva — a field of stone monoliths that the pre-Columbian Muisca people used to track the movement of the sun and determine planting and harvesting cycles. Some of the stones are aligned to cast shadows that mark the solstices and equinoxes; others appear to track lunar cycles.
The site has a small but informative museum at the entrance explaining the Muisca calendar system and the significance of each stone. It is best visited on a clear day, when the shadows are sharp and you can understand how the system worked. Combined with El Fósil and the Ecce Homo convent nearby, it makes a full morning of remarkable sites from very different eras of the region's history.