Archeologists in Moscow have discovered a “secret spy room” buried underneath the streets of the capital.
The room was uncovered in Moscow's central Lyubyanka district during the city's ongoing construction work.
Experts believe the hideaway — called a slukh in Russian — would have been used to spy on the city's enemies in the 16th-century.
Soldiers sitting inside the room, which would have been hidden beneath the walls of Moscow's Kitaygorod Wall, would have been able to hear the conversations of those outside thanks to the den's acoustics.
Similar niches were discovered during the construction of the Moscow metro during the 1920s.
The Kitaygorod Wall was built in the first half of the 16th century to protect the city from raids from Crimean Tatars. The wall once stretched over 2.5 kilometers and featured 12 towers, but only small fragments have survived to the modern day.
The room is just one of "an unprecedented number of artifacts" uncovered by Moscow archaeologists in 2017, according to city officials. More than 150 items dating from the 16th to 19th centuries have been discovered in the Lubyanka and Novaya Ploshchad area, where workmen are currently laying new communication cables.
The artifacts include ceramics, copper coins, bullets, a cannonball and a 16th century arrowhead.