The walls of Amsterdam () were built in the Middle Ages to protect the city against attack. The Medieval walls were replaced with a series of bastions in the 17th century. In the 19th century, the walls were torn down and replaced with the Defence Line of Amsterdam (Stelling van Amsterdam), a fortification line which encircled Amsterdam at a distance from the city.
Remains of the Medieval and 17th-century defenses include the former city gates Waag and Munttoren, as well as the defensive tower Schreierstoren and the watchtower Montelbaanstoren.
History
Earthen walls
Around the year 1300, an earthen wall had been erected behind the Nieuwendijk dike. Traces of this wall were discovered during archeological excavations around Nieuwezijds Kolk in 1994. Following the in 1303, Count William III of Holland withdrew the privilege of Amsterdam to have defenses, forcing the town to remove the wall.
About 40 years later, around 1340, new walls were constructed, both along the western oudezijde ("old side") and along the eastern nieuwezijde ("new side") of the Amstel river. On either side of the town, a moat was dug, and a wall topped by a wooden palisade was then built on the inner side of the moat. When in 1385 new walls and moats were built beyond these original walls and canals, the existing walls became known as Achterburgwal ("back wall") and the new walls were called Voorburgwal ("front wall"). This is how the canals Oudezijds Voorburgwal, Oudezijds Achterburgwal, Nieuwezijds Voorburgwal and Nieuwezijds Achterburgwal got their name.
The city walls had three gates: at the northern end of the Warmoesstraat street at the western end of the Nieuwendijk Bindwijkerpoort on the southern edge of the city, by Spui.
In 1425 the city expanded and a new moat was dug, which still exists as the Singel, Kloveniersburgwal and Geldersekade canals. Along the inner side of the canal, an earthen wall was built with three gates: a new Haarlemmerpoort gate, the Sint-Antoniespoort (now the Waag), and the Regulierspoort (now the bottom half of Munttoren tower).
Stone walls
After visiting Amsterdam in 1481, Emperor Maximilian I decreed that the town was to build stone walls to safeguard against attacks by the Duchy of Guelders and the Bishopric of Utrecht. The city had to pay for the walls itself, and instituted a tax to fund the costly project. Construction started in 1482 and took about 20 years to complete, all in all.
The end result was a brick wall, 5 to 6 metres high, supported by stone arches. The walls encircled the entire town, with the exception of the harbour front on the IJ bay along the northern side of the city. At regular intervals along the walls, a number of semicircular defensive towers were built. One of these towers is still standing, the Schreierstoren, built around 1487.
In 1494, a ceremony was held to mark the completion of the city walls. Ironically, by that time the walls were already antiquated. The walls were built to withstand medieval sieges and attacks with stone cannonballs, but gunpowder and iron had by then come into general use for attacks on walled cities.
The city walls had five gates: Haarlemmerpoort Regulierspoort (now the bottom half of Munttoren tower) Sint Antoniespoort (now the Waag)
In 1512, troops from the Duchy of Guelders attacked the city and looted the Lastage, an area of shipyards beyond the city walls on the eastern side of the town. To protect the Lastage, a new moat was dug in the period 1515-1518. By expanding a branch of the Amstel river, the Nieuwe Gracht ("New Canal", now the Oudeschans) canal was created. The soil produced by widening the river branch into a canal was used to build a wall along the inner side of the canal, topped by a wooden palissade. As part of these new defensive works, the Montelbaanstoren was built around 1516 as a watchtower.
Bastions
During the 17th century, the city expanded rapidly. To protect the grand new grachtengordel (the concentric belt of canals), a system of 26 bastions was constructed along the Singelgracht canal.
Immediately following the Alteratie in 1578, the city began to strengthen the weak spots in its defenses. For instance, a bastion was constructed by the Haarlemmerpoort gate, which at that time lay near Herenmarkt square. William of Orange ordered the fortifications engineer Adriaen Anthonisz to Amsterdam in 1581 in order to oversee the construction of the new defensive works.