Huge cross marks Stalin purges outside Moscow
The wooden cross - 12.5m high (41 ft) and 7.6m wide (25 ft) - was placed in Butovo, at the site of a former execution ground.
At least 20,000 people were killed there by Stalin's secret police, the NKVD. The first killings occurred exactly 70 years ago.
Hundreds of people attended the ceremony south of the capital.
Events marking the 70th anniversary of Stalin's drive to purge opponents of his regime have been held throughout Russia.