If you think San Agustín feels empty, wait until you go to Tierradentro. Few tourists make it to this remote archaeological site, Colombia’s second-most important. While San Agustín is known for its statues, Tierradentro is known for its more than 100 hypogeum, underground tombs that date from the 6th to the 10th century. These burial chambers can measure as much as 12m wide and are carved out of volcanic rock. The walls of many of them are painted with red and black geometric motifs. They are unlike anything else found in the Americas, and the culture that built them disappeared, leaving little record as to who they were. While the tombs show some similarities to the ruins at San Agustín, they are believed to have been built by distinct cultures.