China (Beijing environs)
During its 15th Century heyday, the wall snaked
over 6000 kilometers (3700 miles). A million
warriors garrisoned it to keep out the "barbarians
from the north." The first stone was laid around
500 B.C. and the wall wasn't completed until two
millennia later. Although most of the wall is now
in ruins, the tourist-site portions have been
restored.
Rome Colloseum