Old canal houses are very popular in Amsterdam. Some of these narrow buildings are 500 years old. They lean at very odd angles, adding a certain charm to the city. Once taxes were assessed by the size of the frontage, forcing the thrifty Dutch to build their homes very narrow. Some canal houses are barely wider than the front door! Amsterdam now has strict regulations prohibiting new construction in the historic area (practically the whole central city). So ongoing renovations keep the houses livable. Restored canal houses can be worth millions of dollars.