Tianya Haijiao — literally "Edge of the Sky, Corner of the Sea" — is a coastal park about 26 kilometres west of central Sanya built around two enormous granite boulders sitting just offshore. Chinese calligraphy carved into the rocks during the Qing dynasty gave the site its name, and the phrase has long been a Chinese metaphor for the ends of the earth, used in poems by poets like Su Dongpo (who was himself exiled to Hainan).
The park itself is well-touristed and tightly managed — entry tickets, neat paths, food vendors — but the boulders are genuinely striking, especially at sunset when the sea behind them turns gold. A pleasant beach runs along the inner curve of the bay; the rocks themselves are off-limits but you can wade out for a closer look at low tide. There is a small museum on the cultural history of Hainan exile and a few reconstructed Li ethnic dwellings. It is best combined with a visit to Nanshan Temple, which lies further along the same coast road.