Co Loa Citadel

Less than 30 minutes north of Hanoi is a series of large earthen ramparts that used to protect one of the country's earliest capitals from Chinese invaders. Co Loa, or "snail," so named for the spiral-shape protective walls and moats that resembled the design of a nautilus, was built by An Duong Vuong more than 2,000 years ago and remains one of northern Vietnam's important historical relics.