Amsterdam’s famous canal houses weren’t designed by architects. They were designed by tax avoidance. In the 17th and 18th centuries, Dutch cities taxed houses according to the width of their street or canal frontage. The wider the façade, the higher the tax bill. In response, builders constructed houses that were deliberately narrow - often just three or four metres wide - but extremely deep and tall, sometimes rising five or six storeys behind the slender front. This tax-driven design produced the distinctive Amsterdam canal house: tall, narrow, and topped with a large wooden hoist beam on the gable. Because the internal staircases were often too steep and narrow to carry furniture, belongings were lifted through the windows using ropes and pulleys. What looks today like charming historic architecture was, in reality, a rational response to a punitive tax on width. The results were often impractical. Rooms were long and thin, natural light was poor deeper into the house, and daily life was constrained by the awkward proportions. Yet the tax succeeded in permanently shaping the city’s appearance. It remains a clear example of how taxes do more than raise revenue - they actively distort the human behaviour and the physical world. When governments tax something as basic as the width of a building, people will build around the tax rather than for livability, beauty or common sense. The elegant façades of Amsterdam’s canals are, in part, a monument to tax avoidance.