We take you on a journey to Peru's famed Inca citadel, Machu Picchu. Perched at an altitude of 2,430 metres, this UNESCO World Heritage site still holds many secrets. Some of them were recently uncovered by archaeologist José Bastante and a team of Polish researchers. They found a system of underground aqueducts, as well as other fascinating structures. Our France 2 colleagues report, with FRANCE 24's Monte Francis.