The once-secret bunker, built between 1978 and 1983, is located deep in a pine forest just north of Berlin, and was meant to serve as the command centre for East Germany's National Defence Council in case of war with the West.
The bunker, known as project 17/5001 and code-named Pearl, reeks of humidity with condensation drops trickling from ceilings and, for safety reasons, will be closed again at the end of October.
Groups will be given tours through the ill-lit complex, 50 by 65 metres (164 by 213 feet) large and built over three storeys in depth. Its 170 rooms were meant to accommodate some 400 of the communist state's ruling elite for up to two weeks in case of nuclear war.
But the tourists will not be the first visitors to the bunker.
Shortly after the fall of the East German regime in 1990, metal thieves broke into the complex, stealing miles of electric cable and piping.
At its inception, the bunker was considered the most up-to-date and best-constructed complex of its kind in the Warsaw Pact, outside the Soviet Union.
It was prompted by the arms race which saw the United States position Pershing II and cruise missiles along the Iron Curtain.
"If there had been a blast, the bunker would have immediately been hermetically sealed and would have totally self-sufficient," said Hannes Hensel, one of the tour organizers from the Berlin Bunker Network (BBN) association.
For the first 36 hours after a nuclear explosion, the air would have been completely recycled, and filters would then have allowed people to breathe for 14 days, he said.
Some 85,000 tonnes of reinforced concrete went into its construction and some of its key installations were built on metal platforms able to absorb the shock of nearby nuclear blasts.
The way into the bunker leads through nuclear decontamination locks with a blue-line route for those free of contamination and a red one for those in need of chemical showers and treatment.
"One was supposed to wash off with a chemical solution under the shower for 15 minutes to get rid of radioactive particles or material from chemical or biological weapons," said Hensel.
People then changed clothes and were allowed into the bunker.
Submarine-like tunnels are closed off by heavy metal doors, while some of the living space still has wallpaper attached.
The command centre was equipped with desks and metal lecterns, along with mechanical control systems rather than computer-controlled ones.
Honecker himself is said to have visited the bunker only once, spending just 20 minutes there after it was completed in December 1983.