Archaeologists in Sweden have uncovered the country’s largest Iron Age monument in Old Uppsala , an ancient pagan religious site. The remains of two rows of colonnades dating back to the 5 th century were found during work on a new railway line.

The remains of the pre-Viking foundations include post holes stretching for about 1 kilometre in one row and ½ a kilometre in the other row. They would have held giant wooden poles measuring up to 7 metres in height and which would have needed at least a tonne of rock to support them.

Archaeologist Lena Beronius-Jorpeland said it is Sweden's largest Iron Age construction and said the geometrical structure is unique. However, their purpose is not yet clear. It is possible they are related in some way to the nearby royal burial ground which dates back 1,500 years where the three Iron Age kings Aun, Egil and Adils are believed to be buried.

“It is a completely straight line and they have dug postholes every 20 feet (6m),” she said. “They have had an idea of exactly where this line is going and where to build it.”

Old Uppsala is known as a centre for Norse religion, where believers gathered to sacrifice animals to gods such as Odin and Thor. Beronius-Jorpeland explained that written testimonies from medieval times describe the city as a place for large pagan 'blood ceremonies' and religious feasts. The skeleton of a puppy was discovered in one of the pits, which may indicate that it had been sacrificed there.

It is believed that there are many more colonnades in the area and archaeologists will continue to excavate and analyse the findings.

By April Holloway