The Greeks were astute when they made Cronus, who is Time, a devourer of his own children. Time is, indeed, the Great Devourer and though we may stand in the moment and look upon our monuments thinking that these are proof against the corrosive winds of change, in the fullness of time they, too, shall erode and fade away.
Troy, Abu Simbel, Machu Picchu, Mycenae... all of these places were once great cities. All that remains of them now are ruins and remnants to remind us that there was once a people there who were prosperous and who, like us, could not imagine a time that would not contain them.
Gaze upon this collection of dead cities and ponder that there shall be a time when London, New York, Bejing, and San Francisco shall, too, be nothing more than a faded memory.