You might well call it a fissure, a gap or a chink. But the folks of Reutlingen in Baden-Württemberg, western Germany are adamant that a 31cm (12.2in) divide between two houses is in fact a street. They are keen for the space between house numbers 9 and 11 on Spreuerhofstrasse to continue being recognised as such, if only because the world's narrowest street draws in tourists from around the world.

Visitors aren't necessarily encouraged to squeeze through the 3.8 metre (12.5ft) long divide, but if they insist on doing so are asked to consider in advance how they might extricate themselves should they get stuck. Many try it, despite the unpleasant experience of getting dripped on from the guttering above. Anyone more than 1.8 metres (5ft 9in) is advised to stoop. Some locals are known to refer to the Spreuerhofstrasse Spalt (gap) when they go on diets. As in "once I can fit through the Spreuerhofstrasse Spalt I'll be down to my desirable weight".

The svelte street has existed since 1726 when a devastating fire swept through the city destroying it. Spreuerhofstrasse was rebuilt, but with little regard for the city regulations that stated dwellings should be built far enough apart to prevent any future fires from spreading too fast. Its status was in doubt for years until in 1820 a purportedly slender town hall official, who was able to squeeze down it himself without too much difficulty, declared it to be a public street.

But Reutlingen's top attraction is in danger of losing its Guinness Book of Records status because the wall of No 9 is leaning dangerously into the passageway due to bulging, water-soaked beams. If the gap is no longer passable, and the building cannot be shored up, then it can no longer be considered a street, and its unique status will be revoked. A decision on whether it will be closed has to be made by next year. "Let's face it, if you can't pass down a street then it's no longer a street," says Tanja Ulmer at the tourist office. "There would be no fun left in it then."