Last time we counted, UNESCO had picked out 830 World Heritage sites around the world, chosen for their cultural and historical importance, and also for their geological uniqueness. Ha Long Bay offers a little of all three.

It's not the cliffs themselves that make Ha Long Bay unique, but rather their sheer number. A huge bay, dotted with nearly 2,000 mostly uninhabited limestone cliffs, the breathtaking scenery is very similar to that of the Andaman coast of Thailand, Vang Vieng in Laos and Guilin in China.

Created over millions of years, tectonic forces slowly thrust the limestone above the water-line. During this process waves lapping against the stone carved out a number of vast, striking caverns, as well as other geologically interesting formations, such as tunnel caves and uniquely shaped massifs.

Over the ages, Vietnamese fishermen with too much time on their hands began to see shapes in the stone massifs atop many of the islands, and named the islands accordingly -- Turtle Island, Human Head Island, Chicken Island and so on.

In what constitutes one of the most fascinating cultural features of the area, some of these fisherman still live on the bay today -- on floating fishing villages, where houses are set atop barges year round, the inhabitants catching and cultivating fish throughout.

Ha Long Bay cruises mostly run out of Hanoi or the coastal town of Halong City(which faces out and over the bay). There are hundreds of agencies selling tours on the bay, but very few actually run their own boats -- instead most are consolidators or resellers. Organising a tour is very much a buyer beware scenario -- talk to other travellers and shop around -- if you're paying $15 a head for a two day tour of Ha Long Bay rest assured it will be pretty dodgy. Try to include a stay on Cat Ba Island if you can.