The canal cruise commentaries (usually pre-recorded) love to tell yout that Singel 7 is the narrowest houses in the city. Rubbish, of course. Singel 7 appears to be only as wide as a flight of stairs but it is simply the back entrance of a much bigger house on the Jeroenensteeg on the block behind.
The house at Singel 166 is a real narrow house and built the other way round from Singel 7. It dates from 1634 and was constructed by filling in an old alley between two potteries. In fact it is triangular, sixteen metres deep and with a back wall 5 metres across.