Abingdon Tunnels Underground ammunition bunker in Changi, located at Abingdon and Cosford Roads. The only remaining bunker among those built by the British military for its 15- inch guns (also known as ‘Monster Guns’) just before World War II to protect Singapore against sea attacks, the magazines of the bunker stored 15- inch shells for one of the three guns and their installations which made up the Johor Battery.

When the guns were about to fire, the shells would be moved out of their racks and hoisted up mechanically into the breech of the gun. Each shell weighed about 879 kg, or the weight of a small car, had a range of 34 km, and could be fired at the rate of two shells per minute. The 15- inch gun was directly above the ammunition bunker, which was three storeys deep. The bunkers containing the ammunition for the other guns were about 500 m apart and also had their guns directly above them. The other two 15- inch guns were to the north of the Abingdon Tunnels site. Today one of the runways of Changi Airport runs over the position of the northernmost bunker.

All the 15- inch guns of the Johor Battery were controlled by Changi Fire Command, which, from the top of Changi Hill, directed their fire as well as the firing of smaller 9.2- inch and 6- inch guns. Two 15- inch guns of the Johor Battery were able to turn around and fire on the Japanese attacking Singapore from Malaya. They fired into Johor Bahru and later at enemy troops during the Battle of Bukit Timah. However, the 15- inch gun on top of Abingdon Tunnels could not turn more than 180 degrees. It had been mounted on an older Mark I casing instead of the Mark II casing of the other two guns, which could turn 290 degrees.

The guns were dismantled before the British surrendered in 1942. All the underground bunkers, except the one at Abingdon Road, were removed for the expansion of Changi Airport. The Abingdon bunker had been sealed by the British when they withdrew their forces from Singapore in 1971, but was rediscovered by the Prisons Department in 1991 when they were excavating the site prior to its redevelopment. In 2002, it was marked as a historic site, with a life- sized replica of a 15- inch gun erected on top of the remains of the bunker.