A UNESCO World Heritage Site and a popular day trip from the capital Hanoi, Halong Bay is famous for its limestone karsts and almost two thousand islands and islets that dot the turquoise-green waters. While most of these islands are just towering rocks emerging from the ocean, with no place to land, many make for great climbing destinations or have caves that can be approached with boats.

Only 40 of the islands in Halong Bay are inhabited, and only a few of those are developed enough to offer hotels, restaurants, and recreational opportunities for visitors–including the larger Cat Ba Island, where most of the cruise boats dock. Still, many visitors that arrive in Halong Bay via a cruise spend their nights onboard, using the daytime to snorkel, kayak, or sunbathe.

If you’re considering a trip to the area, discover the best things to do with our list of the top attractions in Halong Bay.