These hills are one of the rarest geological forms on our planet and the most beautiful place in the Philippines. They cover a surface of over 30 square miles on Bohol, the tenth largest island in the Philippines. Most of the time, the hills are green. However, during the dry season or extended periods of drought, they turn into a chocolate shade of brown. There are roughly a thousand hills with heights varying between 100 and 400 feet. They formed around 2.5 billion years ago. There are several theories regarding these hills. One of the theories is that they formed because of tectonic activity that moved and elevated the limestone deposits on the seabed. The mysterious thing about them is that they are very regular in shape, with a perfect symmetry that no one can explain.