Saipan, Guam, and many other islands of the Marianas were all important battle sites during WWII, and many Japanese bunkers and armaments still exist on these islands. These sites are managed by the National Park Service under the "War in the Pacific" Parks designation. Saipan is fairly small and by renting a car or moped, it is easy to drive around the island and take in the natural splendor, as well as visit a number of parks. Scuba diving is also popular, and the underwater world should definitely be seen.
Banzai Cliff
and Suicide Cliff, on the northern tip of the island, were sites where thousands of Japanese civilians, trying to escape the fighting and convinced by the Japanese Army that they would be killed by the Americans, jumped to their deaths in the Battle of Saipan in 1944. The former is by the sea while the latter is on the rock outcropping overlooking it. Numerous Japanese memorials mark the sites.