Neatest abandoned airstrip, bar none has to be the ones on northern part of Tinian. Where the superfortresses, took off to bomb Japan, and the nukes were flown from there. You drive your car rental all over the airstrips there and visit the atomic bomb pits. Pretty abandoned of a time long gone. There was also one on the north end of Saipan, which was pretty heavily conceiled with grass but you knew you were on it.