Diamond Head's Island is the popular name for Oahu, the third largest of the Hawaiian Islands. Oahu is home to the world-famous Diamond Head, a volcanic tuff cone that was formed over 300, 000 years ago. The island is also home to the state capital of Honolulu and the majority of the population of the state of Hawaii. It is a popular tourist destination, offering a variety of activities such as surfing, snorkeling, and hiking.