Ha Long Bay's "Cave of Surprises" houses a popular phallic rock formation.

The notorious "Hanoi Hilton" where Vietnamese colonial subjects and later American POWs, including John McCain, were imprisoned.

A magnificent collection of imperial armor and weaponry.

Giant WWII fortresses that fired 8,000 rounds a minute, now home to thousands of pigeons.

The enormous diamond-shaped building packs a trove of academic and literary treasures into one futuristic space.