I've been to Sanya twice, 2005 and 2007. Actually I will be back to that city soon for another vacation!
Sanya is located on the southernmost tip of Hainan Island, Sanya is the island's most famous tropical resort, wonderful in the baking summer months and also a popular spot in winter too.
Sanya town is situated on a small peninsula, connected to the mainland by two bridges.
This is a great place to soak up some atmosphere and the night market here is especially lively with seafood thrown on the streets, stores selling all types of weird and wonderful wares (including smuggled goods from Vietnam) and huge tea warehouses, all adding to the chaotic feeling about this place.
And it is the beaches that are the biggest attraction here. Sanya has some of the most beautiful and well-maintained stretches of sand not just in China but in southern Asia. The most famous beach in Sanya is located in Yalong Bay. The sand here is white, palm trees provide shelter from the sun and the sea is wonderfully blue and warm. Sanya city beach is crowded with the local people who lived and work in the city. Now that there is more resort in Haitang Bay and growing famous day by day.
This is just about the only place in China with a really laid-back feeling and atmosphere. You could spend anything from a few days to a week or so here, soaking up the sun, relaxing and just enjoying the unique and relaxed ambience that dominates this place.