The Munttoren ('Coin Tower') was originally part of the Regulierspoort, one of the main gates in Amsterdam's medieval city wall. The gate, built in the years 1480, consisted of two towers and a guard house. The name of the tower refers to the fact that it was used to mint coins in the 17th century.
After the gate went up in flames in a 1618 fire, only the guard house and part of the western tower remained standing. The tower was then rebuilt in Amsterdam Renaissance style in 1620, with an eight-sided top half and elegant open spire designed by Hendrick de Keyser, featuring a clockwork with four clockfaces and a carillon of bells.
The carillon was made in 1668 by Pieter Hemony, who added new bells to the instrument that he and his brother François had made earlier for the tower of the Amsterdam stock exchange in 1651. In 1873, the original baton keyboard was removed from the carillon, in favor of changes to the clockwork mechanism. In 1960 a manual playing system and a manual baton keyboard was re-installed. The current carillon consists of 38 bells. A mechanism causes the bells to chime every quarter of an hour.
The guard house is not the original medieval structure but a 19th century replica. The original guard house, which had survived the fire of 1618 relatively unscathed, was replaced with a new building during 1885-1887 in Neo-Renaissance style. An underpass was added to the building during a 1938-1939 renovation.
References:The Walls of Constantinople are a series of defensive stone walls that have surrounded and protected the city of Constantinople (today Istanbul) since its founding as the new capital of the Roman Empire by Constantine the Great. With numerous additions and modifications during their history, they were the last great fortification system of antiquity, and one of the most complex and elaborate systems ever built. They were also the largest and strongest fortification in both the ancient and medieval world.
Initially built by Constantine the Great, the walls surrounded the new city on all sides, protecting it against attack from both sea and land. As the city grew, the famous double line of the Theodosian Walls was built in the 5th century. Although the other sections of the walls were less elaborate, they were, when well-manned, almost impregnable for any medieval besieger.