Montalban Tower. The Montelbaanstoren is a tower on bank of the Oudeschans, a canal in Amsterdam. The original tower was built in 1516 as part of the Walls of Amsterdam for the purpose of defending the city and the harbour. The top half, designed by Hendrick de Keyser, was extended to its current, decorative form in 1606. Since then the tower has been 48m tall. Because the 3rd Duke of Alba proposed incorporating the tower into a castle the tower became known in Dutch as the Monte Albano Toren. Over the years this became garbled to Montelbaanstoren. The castle was never built.