covert space
noun phrase

- a secret room, passage way, or hiding place

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TALKING POINT

For the rich, covert spaces have long offered a guarantee of escape to safety or privacy - the ability to disappear, by slipping behind a door camouflaged a mirror or a bookshelf.

Many of England's castles and country houses had covert spaces for the purpose of concealment or escape and that could be ready at a moment's notice.

In the time of legal persecution the number of secret chambers and hiding-places increased in the houses of the old Catholic families. These often took the form of apartments or chapels in secluded parts of the houses, or in the roof space, where Mass could be celebrated with the utmost privacy and safety. So-called Priest's holes were built in fireplaces, attics and staircases and were largely constructed between the 1550s and 1605.

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NOTABLE NUMBERS

$10,000: Base price for installing a secret room in your house, according to Creative Home Engineering, an Arizona firm that specializes in clandestine architecture.

12: Highest number of concealed doors the same firm has built in a single house, according to lead designer Travis Humble.

2,600 feet (792 meters): Length of the Passetto di Borgo, a tunnel at the Vatican, once used by popes to flee from foes.

2,640 ft (805 meters): Length of the longest known tunnel ever built under the US-Mexico border. It ran from a house in Tijuana to an ersatz wooden pallet business in San Diego.