The islands of the bay are divided by a broad channel: to the east are the smaller outcrops of Bai Tu Long, while to the west are the larger islands with caves and secluded beaches. Among the more spectacular caves are Hang Hanh that extends for 2 km. Tour guides will point out fantastic stalagmites and stalactites which, with imagination, become heroes, demons and animals. Hang Luon is another flooded cave that leads to the hollow core in a doughnut or Polo-shaped island. It can be swum or navigated by coracle. Hang Dau Go is the cave wherein Tran Hung Dao stored his wooden stakes prior to studding them in the bed of the Bach Dang River in 1288 to destroy the boats of invading Mongol hordes. Hang Thien Cung (Heavenly Palace) is a hanging cave, a short 50-m haul above sea level, with dripping stalactites, stumpy stalagmites and solid rock pillars. A truly enormous cave and one of those most visited is Sung Sot Cave (Surprise Cave).
The World Heritage Site is best explored on a boat trip from Halong City or, better still, from Cat Ba island which occupies a stunning setting in the south of the bay. Despite the growth in numbers of karaoke-loving weekenders Cat Ba remains an attractive place but best of all it is a great springboard into the surrounding waters of Halong Bay and an increasingly popular alternative to Halong City. The chief advantage is that there is a lot to see on the island including the stunning scenery of the interior.