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
Italy (Rome)
Remarkably, despite the ravages of nearly 2000
years of weather, wars and urban development,
the historic Roman Colloseum stands in its
present condition. Up to 50,000 roaring
spectators were entertained -- sometimes by
gladiators fighting to the death humans and fierce
wild animals.