historian Geert Mak calls it – and not from the centre outwards, as a popular myth has it. The canal construction in the southern sector was completed by 1656. Subsequently, the construction of residential buildings proceeded slowly. The eastern part of the concentric canal plan, covering the area between the Amstel river and the IJ bay, has never been implemented. In the following centuries, the land was used for parks, senior citizens' homes, theatres, other public facilities, and waterways without much planning. Over the years, several canals have been filled in, becoming streets or squares, such as the Nieuwezijds Voorburgwal and the Spui. Expansion After the development of Amsterdam's canals in the 17th century, the city did not grow beyond its borders for two centuries. During the 19th century, Samuel Sarphati devised a plan based on the grandeur of Paris and London at that time. The plan envisaged the construction of new houses, public buildings and streets just outside the Grachtengordel. The main aim of the plan, however, was to improve public health. Although the plan did not expand the city, it did produce some of the largest public buildings to date, like the Paleis voor Volksvlijt. Following Sarphati, civil engineers Jacobus van Niftrik and Jan Kalff designed an entire ring of 19th-century neighbourhoods surrounding the city's centre, with the city preserving the ownership of all land outside the 17th-century limit, thus firmly controlling development. Most of these neighbourhoods became home to the working class. In response to overcrowding, two plans were designed at the beginning of the 20th century which were very different from anything Amsterdam had ever seen before: Plan Zuid (designed by the architect Berlage) and West. These plans involved the development of new neighbourhoods consisting of housing blocks for all social classes. After the Second World War, large new neighbourhoods were built in the western, southeastern, and northern parts of the city. These new neighbourhoods were built to relieve the city's shortage of living space and give people affordable houses with modern conveniences. The neighbourhoods consisted mainly of large housing blocks located among green spaces, connected to wide roads, making the neighbourhoods easily accessible by motor car. The western suburbs which were built in that period are collectively called the Westelijke Tuinsteden. The area to the southeast of the city built during the same period is known as the Bijlmer. Architecture Amsterdam has a rich architectural