The very rich in Manhattan live in apartments as big as presidential suites, to which they ascend in tiny walnut-panelled elevators.
Guests are escorted through marble-floored hallways with classic statues to reception rooms hung with pieces of art, and on to a dining room with a table for up to two dozen guests.
They might glimpse a couple of family rooms, a tiled kitchen big enough for a restaurant, a pantry and a maid's quarters. But in some apartments there is one room the guests never see.
It is hidden behind a book case or a bedroom closet and can be opened only with the high-tech equivalent of the secret lever that swung back a panel into the keep of a medieval castle.
This is the "panic room", a hermetically sealed self-contained refuge from intruders, installed by paranoid residents on the Upper East or Upper West Side.
The most expensive version has steel walls and is likely equipped with closed-circuit television monitor, refrigerator, emergency generator, gun, microwave oven, portable toilet, flashlight, telephone and perhaps a bottle or two of fine wine.
The secret vaults of Manhattan's rich have suddenly come to the public's attention because of the film Panic Room, which is currently the No 1 box office hit in the US, grossing $73 million (€82 million) in three weeks.
In the movie, the divorced Jodie Foster character and her daughter are forced to rush to the secret room on the very first night in their new Brownstone apartment, as three intruders enter the premises.
What the villains want is actually inside the safe room, which they know about, and they proceed to try to break down its defences (the emergency telephone, needless to say, did not work).
This Hollywood nail-biter is stimulating business for the companies that install what are known in the trade as "safe rooms" at prices ranging from $25,000 for a small hide-away to $2 million for the real thing.
The average panic room installed by CitySafe, a firm based in Farmingdale, New Jersey, reportedly costs $1.2 million, but for that one gets not just an impregnable biosphere but a counter-attack mechanism consisting of high intensity flashing light that can make you throw up and piercing ultra-sound that can knock you out. About 100 safe rooms have been installed in Manhattan in the past decade.
The latest models are constructed not from concrete and steel but lightweight Kelvar that can stop armour-piercing bullets and is much cheaper.
Business for the three main companies that install the rooms in Manhattan buildings was facing a turn-up before the movie because of the terrorist attacks, which have heightened the sense of insecurity of New Yorkers.
The film company has hyped the atmosphere further with what it claims is the growing popularity of panic rooms in "our increasingly dangerous world".
Those who worry most about their security from assassins, thieves and kidnappers are said to be big-name entertainers, super-rich investors and diplomats, though it seems that across the United States the biggest demand is from homeowners who are more concerned to have a cement and steel retreat that will withstand hurricanes and tornadoes.
Builders in New York understandably refuse to name their clients or show reporters their work. It is no use putting in a secure room in a luxury apartment if everyone in the building knows about it. Construction work is divided among different suppliers so that no one gets to know what is being installed.
Company workers do not wear uniforms and come and go at odd times through side doors.
This way the concierge, the maid, the nanny or anyone else do not get to know what is going on so that in a crisis they cannot be made to talk.
That is why if you are ever invited to one of these Manhattan apartments, you will not be shown the secret room no matter how friendly you are with the host.
Better just go and see the movie, which incidentally shows just how unsafe a panic room can be, unless that is you have Jodie Foster with you figuring out how to repel the baddies.
