It took over one thousand years to build the city of Sanchi, but its decline came following the fall of Buddhism within India. The city was rediscovered by the British in 1818.
Teotihuacan, built within the 2nd century B.C., was located within the valley of Mexico. The city featured a decline in population during the 6th century, where the pyramids of the lost city were honored by the Aztecs. They are a place of pilgrimage now.