Machu Picchu Citadel, Cusco Region — the royal estate of Sapa Inca Pachacuti, built without mortar, iron, or the wheel from perfectly fitted granite blocks. Abandoned around 1572 and lost to the outside world until 1911, it remains the best-preserved Inca city on earth.
© Martin St-Amant (S23678), CC BY-SA 3.0, via Wikimedia Commons
