The USSR launched five missions (Zond 4-8) between 1968 and 1970, apparently as tests for a manned Moon landing, but the exact purpose of the missions has never been fully revealed to the scientific community.
The Soviet lunar program was dropped 3 years after U.S. astronauts Armstrong and Aldrin made it to the Moon and back.
The Soviet program seems to have depended on creating a new booster rocket.
The N-booster, as it was known, used a total of forty-four rocket engines in five stages to send a two-man Soyuz spacecraft to orbit the Moon and a one-man lunar module to land.
Rather than use a tunnel to reach the lunar module in space, a cosmonaut would have had to make a dangerous space walk to enter it.
The Soyuz spacecraft never made it to the Moon, but it has been a very useful vehicle in Earth’s orbit.
Soyuz derivatives provide Russia’s human spaceflight capability and are used to ferry personnel and supplies to and from the International Space Station.