If you're a war buff or have relatives who fought in WWII in Asia, the Changi Museum is worth a visit. Located near the airport, what is now the Changi Museum building was a prison for POWs during the Japanese occupation of Singapore. Through old photos, letters, drawings, and personal effects, the museum chronicles the struggle of the POWs and civilians who were imprisoned there. There are detailed maps of the Japanese incursion in the region and displays of WWII artifacts and personal belongings of POWs. It's easiest to reach by taxi, though you can get there via a combination of MRT and bus.