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This page contains excerpts from several sources. It is added as background information for a write-up of a trip to Pampus.
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Fort island Pampus


Fort Island Pampus was built between 1887 and 1897. The fort on an artificial island in the middle of the IJmeer was once part of the Defence Line of Amsterdam, a 135-kilometer-long system of fortifications that defended the city by means of flooding.

Even before the island Pampus was built as part of the Defence Line, the shallows – then known as Pampus sandbank – held a significant place in Dutch life. Trading ships from the Dutch East Indies loaded with spices, tea and silk would anchor off Pampus, because they often were too heavily loaded to sail over the shallows into the port of Amsterdam. Here the crew would wait until either the goods would be landed or the ship would be lifted higher out of the water by so-called ‘ship camels’ – flotation tanks – so she could sail into port.

The ship camel was invented in 1690 to allow large ships of the line to cross shallow banks that isolated the harbour of Amsterdam from the open sea. The camel was mostly used in the Dutch Golden Age for accessing the shallow waters at Pampus, which were unreachable for large merchant ships.

Pampus, map 1628
Pampus, map 1628
Ship camel
Ship camel

When the Defence Line of Amsterdam was built at the end of the 19th century, the fortress island Pampus was constructed. The first stage of the building was to lay down a work platform where the centre of the fort would stand. The vast quantities of material were delivered by ship out of Amsterdam. A German Company built the steel gun turrets.

Construction Pampus Island
Construction Pampus Island

How the island of Pampus was constructed

Piles, foundations and cisterns (R=cistern)

The specification of 10th July 1889 stipulated that there were to be eight test piles driven with a total length of a 110 metres, and 3860 piles, probably of pinewood, each pile 11 metres long, to support the fort. According to the drawing above, a copy of the original piling plan, there should be 3852.

Under each turret were 117 piles. What strikes you about the drawing is that there are no supports shown under the counterscarp wall and the dry moat. The circumference of the piles at one metre from the top of each pile and to be not less than 0.85 metres under the bark, and at the point of the pile, not less than 0.4 metres.

A few dimensions: (NAP = Normal Amsterdam Level - Dutch Ordnance Datum)

Length of island205mLength of Main building86m
Breath of island164mBreatchc of Main building36.8m
Ht of slope, north side+6.5m NAPLength of dry moat245m
Ht of slope, south side+5.45m NAPBreath of dry moat8.20m
Ht of top of cupolas+11.02m NAPThickness of roof (middle)6m
Ht of roof in middle+9m NAPThickness of northern wall14m
Ht of poternes+3mHeight of lightning+13.34m NAP
Ht of fog bell+12m NAPHeight of chimney+12m NAP
An oval hole was dredged with an area of around 10.75 hectares. 35,000 cubic metres of silt and clay was excavated and removed.
The hole was then filled with around 43,000 cubic metres of clear sand taken from the Muiderzand bank near Muiderberg.
After a period of settlement and consolidation the excess sand was again partially dredged and used to heighten the glacis.
Piles were driven into the hole thus was created and eventually the fort with 80 compartments was built. At a distance of 16 metres from the island fort a submerged barrier of rocks was positioned. This 675 metre-long obstruction served not only as a breakwater but also to prevent enemy ships from landing on the island. The top of this breakwater lies currently about 25 centimetres below the surface.
21,725 cubic metres of concrete were used to build the counterscarp buildings, the counterscarp wall, dry moat, poternes and the roof of the main fort building. 2,926 cubic metres of brickwork were used for the walls of the main building and other masonry such as privies, etc.

When Fort Pampus was originally built, it was armed with four Krupp 250 mm guns that fired a shell for a range of 8 km. It included other positions for various guns such as the 57 mm quick firing guns or the M90 Gardner machine guns. There was enough space for 200 men that where in the building while defending the country from the enemy in the First World War. Aerial warfare made the fortress obsolete; still, the world wars did not go by unnoticed.

Pampus drawn on a map from 1892
Pampus drawn on a map from 1892
View of Pampus, 1893
View of Pampus, 1893
Eastern gun turret under construction
Eastern gun turret under construction
Transport of armor plates to the fort
Transport of armor plates to the fort
Unloading armor plates at the fort
Unloading armor plates at the fort
Placing the armor plating
Placing the armor plating

The Wars

Although Pampus was built under the orders of the Dutch Ministry of War it was never used in any wartime actions. The fort was manned during the First World War and in peacetime only the Fort Watcher lived on the island. Fort Island Pampus was closed in 1933.

A deserted and plundered fortress

During the Hunger Winter of 1944/45 it was very cold and the lake froze over so the island became reachable over the ice and the people from Amsterdam stripped all the wood off the island to burn for warmth. Before then the Germans, who occupied the island for a while, stripped all the metal from the island for their war industry. The fort then fell into ruin. In 1962 the island was occupied for a time by students. The remains of their visit can still be seen in the many slogans and wall paintings they left behind.

The start of the Charity

At the end of the 1980’s five people from Muiden decided that the deterioration of the island had to stop. On 20th February 1990 the island was eventually sold by the Netherland’s State to the Charity. The restoration could begin. With a large volunteer workforce the fort was freed from all the rubbish, rubble and undergrowth.


Pampus is visited yearly by many tourists. Pampus has now grown into a tourist attraction. Fort Island Pampus would not be what it is today without the help of the many hands. Thanks to the years-long input from volunteers, the fort has become a valuable monument. These volunteers have made their place in history. Pampus opened on the 8th of July 2011 as the first National Visitors Centre of the Defence Line of Amsterdam.

Defence line of Amsterdam

The Defence Line of Amsterdam (Stelling van Amsterdam) is a 135 km ring of fortifications around Amsterdam. It has 42 forts that are 10-15 km from the centre and lowlands, which could easily be flooded in time of war. The flooding was designed to give a depth of about 30 cm, too little for boats to cross. Any buildings within 1 km of the line had to be made of wood so that they could be burnt and the obstruction removed.

Stelling van Amsterdam
Stelling van Amsterdam

The Stelling van Amsterdam was constructed between 1880 and 1920. The invention of the aeroplane and tank made the forts obsolete almost as soon as they were finished. Many of the forts now are under the control of both the town councils and the nature department. They may be visited by the public, and admission is free on Monuments Day, the second Saturday in September.

The Stelling van Amsterdam was primarily a defensive water line. In the event of an enemy attack, large tracts of land around Amsterdam would be inundated with water, preventing the enemy from advancing. Amsterdam would function as a national redoubt or reduit, as the last stronghold of the Netherlands. Forts were built in which roads, railways or dikes crossed through the water line. At such locations, there would be no water to stop the enemy and so the forts were intended to shell the enemy.

The Stelling van Amsterdam has never seen combat service and the use of aircraft rendered it obsolete after World War I. It was, however, maintained and kept in service until it was decommissioned in 1963.

(Detailed map of the Defence line of Amsterdam)

Visiting Pampus (1) Visiting Pampus (2) Sights of Pampus

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