The Stone Forest (Shilin), China Many of the trees within the forest in China’s remote Yunnan Province are rock hard, literally. The area, which spans nearly 200 square miles, was underwater 270 million years ago, and the sea floor was covered with limestone sediment. Gradually, the seabed rose and the water dried up. As rain and wind eroded the weaker rock, the stronger limestone spires began to take shape. Now they rise skyward, surrounded by leafy trees.