Latvian and NATO troops are using a former Soviet secret city for close combat training - 18 years after the Cold War settlement was abandoned. 

Skrunda-1, in northern Latvia, was a 'closed administrative territorial entity' or ZATO (Russian acronym) which was established in the communist-era to support sensitive military bases and research sites. 

In its prime, the town played a crucial part in the Soviet Union's defence strategy and was home to 5,000 soldiers, scientists and their families. 

Skrunda-1 was built around two 'hen-house' early warning radar stations, which scanned the skies of western Europe for incoming nuclear warheads. 

No traces of the classified city could be found on any official maps or documents and it was well hidden by dense birch forests. 

The 100-acre site featured a labyrinth of buildings, factories, apartment blocks and even a gymnasium and nursery.

Following the collapse of the Soviet Union and Latvia's independence, the site was abandoned in 1991, with its last residents leaving in 1999. 

More: Dead Space & Ruins: The Decaying Legacy Of The USSR