AT the height of the Cold War it was one of the region's best-kept secrets, hidden in what was then an orchard in a city suburb.

But times change and old fears fade - and now the semi-submerged nuclear bunker could even become a tourist attraction.

The stark and stolid structure in the Acomb area of York has become the first building of its kind to be designated a scheduled monument by English Heritage.

The bunker was built in 1961 and less than a year later was at a state of full alert as the world hovered dangerously near disaster during the Cuban missile crisis.

The airtight and bomb-proof subterranean rooms and corridors could accommodate up to 60 people, mostly women, for two weeks or even longer if necessary.

It was the reporting centre for a cluster of bunkers. The role of the scientists and meteorologists within was to gather data on the location and strength of nuclear blasts and radioactivity levels.

But by 1991 it was a relic of a paranoid age, and the following year it was abandoned after the signing of a non-aggression treaty with the Warsaw Pact.

Now the paint is peeling and damp is in the air, but the ambience behind the steel blast doors remains, helped by many of the fittings still being intact, including the ominous operations centre complete with its charts for blast totals.

The bunker is in the grounds of Shelley House, a building which has been used over the years by a number of Government agencies.

The property is now surplus to requirements and is to be sold - and with the bunker a protected building, the likelihood is that it could become a museum. English Heritage's assistant regional director John Hinchcliffe said: "Some buildings are protected because of their intrinsic or architectural merits, but the significance here lies in it being the best preserved bunker of its type in the country."

To mark the scheduling, there will be free tours of the bunker on September 16 between 11am and 2pm. To book, ring (01904) 601901.