CRUMBLING walls. Breathtaking temples. Mysterious cities built entirely underground.
They are the astounding feats of architecture that have been left to decay for centuries.
But while they may be in ruins, the sites of the world's most ancient and intriguing cities continue to wow travellers.
From the popular Machu Picchu site in Peru, to the Pompeii ruins and the lesser-known Derinkuyu site in Turkey, here are eight amazing ruined cities that remain shrouded in mystery - or remain perplexing to this day, according to the science website io9.com.
One thing's for sure, the world is a fascinating place.
starts with :
1. Palenque, Mexico