three of the canals are mostly for residential development (Herengracht or ‘’Patricians' Canal’’; Keizersgracht or ‘’Emperor's Canal’’; and Prinsengracht or ‘’Prince's Canal’’), and a fourth, outer canal, Singelgracht, for purposes of defense and water management. The plan also envisaged interconnecting canals along radii; a set of parallel canals in the Jordaan quarter (primarily for the transportation of goods, for example, beer); the conversion of an existing, inner perimeter canal (Singel) from a defensive purpose to residential and commercial development; and more than one hundred bridges. The defensive purpose of the Nassau/Stadhouderskade was served by moat and earthen dikes, with gates at transit points but otherwise no masonry superstructures.