By Helen Fawkes
BBC correspondent in Kiev
Yuriy uses both hands to heave open the door. This is no ordinary door, but a metre thick barrier at the end of tunnel deep underground.
Some former rocket silos are now functioning museums
The passage way leads to the command centre at what used to be one of the most top secret military bases in the former Soviet Union.
Surrounded by fields of wheat and soya in the countryside of southern Ukraine, there are 10 empty nuclear rocket silos.
Inside what is now a museum, tourists are able to press the button which would have launched a nuclear strike against the United States.
Yuriy used to look after the missiles during the Cold War but now works as a tour guide at the Strategic Rocket Base in Pervomaisk.
"It's always been a great mystery to people, what was happening behind the Iron Curtain," says Colonel Yuriy Yevtushenko.
"Getting to this place was impossible. No one from this country was allowed to this base, not even military people."
But now its doors are open seven days a week.
Tourists see how the USSR could have launched a nuclear strike
Ukraine is celebrating 13 years of independence from the USSR on Tuesday, but the country's underfunded military is struggling to cope.
Defence Minister Yevhen Marchuk has admitted that Ukraine's army is so poverty-stricken that it is a danger to its own people.
He claims the military has not bought a single tank or aircraft since 1991.
One thing it has acquired though is a bad reputation for accidents.
A fighter jet crashed into a crowd at an air show two years ago, a passenger plane was mistakenly shot down during an exercise in 2001 and the year before that, a stray surface-to-surface missile hit a Ukrainian apartment block.
Since independence, hundreds of people have died in military accidents.
"The situation is very bad. Unfortunately, the Ukrainian army has got many problems which have been getting worse for a long time," says a Ukrainian military analyst, Valentyn Badrak.
Ukraine also has 2.5 million tonnes of Soviet munitions which it can scarcely afford to decommission.
There are almost 200 arms dumps and in May one of them exploded in southern Ukraine, causing some $500m of damage.
'Top tourist attraction'
Former top secret military bases are being opened up and it is hoped this will add to the military's coffers.
Tours are offered to explore the tunnels of a submarine base
Dotted along the Crimean coast are three discreet entrances to a massive man-made cave.
Engineers who constructed the Moscow metro buried deep inside a hill which overlooks Balaklava Bay to build a submarine base.
This is where nuclear subs from the Black Sea Fleet were kept hidden.
The base was considered so highly classified that civilians were banned from coming within at least 30 kilometres (19 miles) by the Soviet authorities.
Visitors are now actively encouraged.
But tourists can only see the base by torch, as there are no proper lights yet.
Groups are taken through a locked metal gate complete with hammer and sickle.
The guide leads them through long, cold tunnels.
The floor is criss-crossed with rail tracks which were used to transport the nuclear weapons.
This is set to become a top tourist attraction in the Crimea.
"It's almost like being in a James Bond 007 movie," says Alan Dudley, a holiday-maker from Canada.
"To see this facility, you can just imagine the things that went on during the Cold war, the secrecy, it's thrilling to be here, it's really exciting, I wanted to come here for a long time."