Cracroft Caverns, also known as the Cashmere Caverns, are a series of large chambers in the Cashmere Hills of Christchurch, New Zealand. Rising above the southern end of the city of Christchurch in New Zealand’s South Island is the suburb of Cashmere. ... Christchurch is the largest city in the South Island of New Zealand and the third largest urban area in the country. ...

Constructed secretly during the Second World War in response to the Japanese threat, they were intended to house operational headquarters in the event of attack. The military commandeered the Cracroft Wilson estate, founded by Sir John Cracroft Wilson in 1854, for their Southern Group headquarters, and work on the tunnels began in 1942. Mushroom cloud from the nuclear explosion over Nagasaki rising 18 km into the air. ...

Railways were built for access and for the removal of waste soil. The largest cavern was 7 metres high, 10 metres wide and 30 metres long. Prestressed concrete was used to line the caverns. Officers based in the estate house would come down stairs into the tunnels, while others were to enter through the access tunnels. Construction came to a sudden halt in 1944 as the threat of invasion receded, even though work on the bunkers was nearly complete.

The weekend before the military left the estate, fire broke out and the beautiful Cracroft Wilson House was burnt to the ground. The entrances to the underground complex were sealed after the war, and the existence of the caverns was largely forgotten until excavations were carried out in 1987. The caverns have now became the home of a series of ring laser experiments set up by the University of Canterbury's physics department. Note: This page does not refer to a fiber optic gyroscope, even though the user is directed here when seaching for that term. ...

There is now an associated small public park behind the Princess Margaret Hospital, and parts of the caverns are periodically open to the public. Princess Margaret Hospital is located in downtown Toronto, Ontario, Canada on University Avenue at College Street. ...

References

• General information
• Current ring-laser research use
• Location