One of the most popular caves for day trips, a visit to Thien Cung starts from the crowded dock area where wooden walkways lead to steep stairs going up to the mouth of the cave -- just a short walk. The interior is a cavernous space, with hokey circus lighting, lots of big rock formations, and the usual interpretive names. This is considered the Cave of the Dragon, where the dragon who created Halong sought refuge, and guides are quick to point out one elaborate stalactite that looks like a dragon (or maybe a hoagie, depending on your interpretation). There's a legend surrounding the cave about a young girl who, in order to end years of oppressive drought, married the presiding dragon in the cave, and their wedding was attended by all in the animal kingdom. Brave girl. It is a "dead cave" in that, unlike many limestone caves, it is no longer dripping water and growing formations of additional deposits or creating new fissures and caves. Lit like a Vegas casino, this is the first cave most visitors reach on the way to Cat Ba Island.