The essential experience at Ha Long Bay is a boat cruise through the limestone karst landscape — either a day trip from Ha Long City or, far better, an overnight cruise on one of the traditional wooden junks. Overnight trips allow you to wake up among the islands in the early morning, before the day-trip boats arrive. Kayaking is one of the best ways to explore: paddling through sea caves, into hidden lagoons, and around the base of limestone towers that rise straight from the water. The islands around Luon Cave, Ba Trai Dao, and Ba Ham are well suited to kayaking. Cat Ba Island, at the southern end of the bay, has a national park with hiking trails and a small beach.