Koko Crater is in east Oahu in the Hawaii Kai neighborhood.  The hike starts at Koko Head District Park at the end of Anapalau St.  Park near the tennis courts and follow the walking path to the bottom of the old rail track.  The trail isn't very long (about 1100 yards / 1000 meters) but the challenge is the elevation rise of 1000 feet.  Hikers walk on the rail ties or you can walk to the side of the tracks.  There is short 30-foot section suspended above a gully that can be scary or tricky for some.  The 1200' summit of Koko Crater provides an awesome 360 degree view of eastern Oahu and the Pacific which makes the hike worth the effort.  Compared to Diamond Head, this is more challenging and parking is free. Best time to go is early in the morning before the sun gets too high in the sky  - bring water and wear sunscreen & a hat!  This hike can get very crowded, especially on weekends. This hike is not for little kids or for anyone afraid of heights.  The rim is very narrow in places and volcanic rock in Hawaii is dangerously crumbly.  Postpone this when it's very windy or rainy

Koko Crater is often mistaken for Koko Head, which is the shorter 640' volcanic cone just a mile south, with Hanauma Bay inside the crater on the east  side of the summit, and the toney Portlock area of Hawaii Kai on its western slopes.Rail Track hike up Koko Head