The Archaeological Park of Tierradentro is a fantastic site and seeing the tombs is a great travel experience as they are quite unusual. A guide for the tombs is useful as the route up the mountain is not marked and the area is very quiet. Once you reach the sights you descend into the individual tombs down very steep steps carved from the rock so make sure you wear sensible shoes/ trekking sandals and trousers/shorts that are easy to move in, and take plenty of water.