The document discusses several canals and landmarks in Amsterdam. The Singel originally encircled the city in the Middle Ages. Herengracht was the first of the major canals built in the city center. Keizersgracht is the second and widest canal between Herengracht and Prinsengracht, which is the fourth and longest of the main canals. Other landmarks mentioned include Magere Brug bridges, the Anne Frank House, the Rijksmuseum, and houseboats along the canals.