Great Wall of China

from The American Heritage® Dictionary of the English Language, 5th Edition.

• A line of fortifications across northern China. Originally built during the Qin Dynasty (221–206 BC) by connecting earlier fortifications, it was subsequently rebuilt and altered many times. The wall reached its greatest extent during the improvements of the Ming Dynasty (1368–1644), when it was expanded to about 6,400 km (4,000 mi) long.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• proper noun An ancient Chinese fortification, almost 4,000 miles long, originally designed to protect China from the Mongols.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a fortification 1,500 miles long built across northern China in the 3rd century BC; it averages 6 meters in width