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Ismantorp House Walls.

Ismantorp Fortress: An Ancient Ringfort Surrounded by Nine Worlds


The Ismantorp fortress on Öland, has been described as one of the most interesting prehistoric defensive structures and one of the most remarkable ringforts in Sweden. Not the largest of the forts, although possibly the oldest, scientists have been debating Ismantorp’s true purpose for years. No evidence of occupation has been found and it was almost certainly deliberately destroyed.

Öland, a long and narrow island in the Baltic Sea just off the coast of Sweden, is famous for its well preserved ringforts of which there are 15 on the island. They are regularly spaced, vary in design and size, and virtually every characteristic of Ismantorp can be found in one or more of the other 14 ringforts.

Oland within the Baltic Sea (Google Maps)

Ismantorp is located in the center of Öland and lies less than two miles from the nearby town from which it now takes its name. The Mittlandsskogen forest surrounds the hill on which the fort was built and the land is largely marsh.

This particular ringfort is one of the better preserved ruins and although archeological excavations continued up until the 1940s, little is known about the site as the research returned meager results – a few pieces of iron slag, shards of undecorated Iron Age pottery, burnt animal bones, and charcoal.  

The limestone ringwall which surrounded nearly 100 homes is approximately 13 feet high (4 meters), 1,300 feet (400 meters) long, and has nine gateways in total.

Studied Since The 1600s, The Ismantorp Fort Hasn’t Easily Revealed Its Secrets

Swedish archeologist, Mårten Stenberger (1898-1973) proposed that Ismantorp served as a place of refuge during the Migration Period (400-550 AD); in the 1970s, scientists speculated that the ringforts acted as fortified villages; and Andrén proposed in 2006, along with other theories, that they served as a location for initiating warriors. The theories have been numerous and varied.

The fort’s nine gates would have made it difficult to defend regardless of the fortifications and a once fortified village would have revealed evidence of occupation.

Ismantorp Entrance Gate (Public Domain)

Ismantorp Entrance Gate (Public Domain)

After the ringfort of Eketorp was fully excavated in the 1970s and artifacts were uncovered, more modern theories arose and previous hypotheses about Ismantorp have been reevaluated.

Built within a mile or two of several villages, the main gates faced the nearest village and although they had similar layouts, their function varied from one fort to another as well as over time, depending on need.

All Roads Lead to the Center of the World

From the third century onwards, Scandinavian military culture changed. Before this period, armies were small groups of individually equipped men and it’s possible that some Scandinavian soldiers serving in the Roman army returned with new knowledge - armies became larger and more organized, weapons were mass produced, and soldiers professionally trained. The Scandinavians may have based their military on Roman models, but the strategies they selected were changed to suit their own beliefs.  

Satellite Image of Ismantorp (Google Maps)

Satellite Image of Ismantorp (Google Maps)

With this in mind, it’s possible to understand the meaning and function of Öland’s ringforts foundations.

During the construction of Roman forts, they determined the ‘center of the world’ and dug a pit. From this midpoint, towns and garrisons were laid out in a square or rectangular fashion and the hole was then filled. At Ismantorp the gates ran towards the geometrically centered pit, although their design was circular and the hole was left open as it represented Urd’s well (well of fate) which was traditionally located in the middle of the world beside the central pillar (the world tree).

The one gate at Ismantorp, which didn’t have unobstructed access to the central area but rather led into a building, served as the route through which to transport the dead to either Hel or Valhalla which both surround the central world tree.

“Valhalla” (1905) by Emil Doepler (Public Domain)

“Valhalla” (1905) by Emil Doepler (Public Domain)

While many Roman camps became civilian settlements over time, the same is not true for many Scandinavian forts since the harsh landscapes were more suited to martial culture than permanent family settlements.

Significant Number Nine

The number nine appears over and over in Norse mythology and arises frequently at Ismantorp (as well as Eketorp and Gråborg). Nine is associated with cosmology and ritual perfection, a transformation from one stage to another.

Nine stone circles at Ismantorp may symbolize a connection between war, rituals, and Norse cosmology. What’s more, the fort’s central post (the world tree) was surrounded by nine gates (the nine worlds).

Yggdrasil, The World Ash of Norse Mythology (Public Domain)

Yggdrasil, The World Ash of Norse Mythology (Public Domain)

Nine commonly occurred in rituals. According to legend, large sacrificial feasts were held every nine years for nine days. Nine men and nine male animals were sacrificed at Gamla Uppsala.

Little more was found during archeological excavation during 2000 apart from an arrowhead and an iron buckle. This raises the question of whether the fort could have been used to train and initiate new warriors or to hold feasts and drinking ceremonies intended to reinforce bonds between warriors from different settlements, much like the Norwegian tun sites.

Ringforts could also have been used to house livestock and slaves stolen during raids or because they were impressive, they could have had an outright purpose of deterring counter-raids.

Whatever the initial purpose, Ismantorp remains an archeological enigma and a popular tourist destination.

Top image: Ismantorp House Walls. Source: Public Domain

By Michelle Freson


Andren, A, 2014 : Tracing Old Norse Cosmology: The World Tree, Middle Earth and the Sun in Archeaological Perspectives (Vagar Till Midgard). Nordic Academic Press.

Available at:  Amazon
Andren, A, Fischer.S, Liden.k, Viberg,A. Victor.H. 2014: The ringfort by the sea: Archaeological geophysical prospection and excavations at Sandby Borg (Öland). Researchgate

Available at:

Bradley, R. 2012: The Idea of Order: The Circular Archetype in Prehistoric Europe. OUP Oxford.

Available at: Amazon

Ismantorp Castle. EnjoySweden

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Michelle Freson's picture


Michelle Freson is a professional writer and editor and has spent many hundreds of wonderful hours working with and learning from fiction writers based all over the globe.

Born in July, 1971, Michelle has long since stopped working out her... Read More

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