A mysterious structure found at the Roman town at Caistor St Edmund, near Norwich, has been described by an archaeologist as 'looking like a spaceship'.

The Roman town of Venta Icenorum, meaning market of the Iceni people, was discovered during the 1929-35 excavations and has been a popular place of both local and national interest, with the BBC's Time Team filming there in 2010.

The latest revelation, dating back to third century AD, was discovered by the Norfolk Archaeological Historical Research Society and has recently been unveiled in an academic journal.

The structure shows two angled wings, meeting on a central structure, and is described by Professor Will Bowden, who has been working on the project from the University of Nottingham, as 'an unusual and adventurous building on a very interesting site'.

The plan of the building was identified through aerial photographs, after weather conditions in 2007 revealed a number of unusual crop markings showing a building, without any obvious similarities to other Roman Britain plans.

Prof Bowden, who studied for his PHD at the UEA, said: 'From the air, it looks like a spaceship, and I'm sure some people will suggest it to be some kind of alien landing site. It is very hard to make any parallels to anything else we've ever seen, we can usually make comparisons, but this one is very unusual.'

It is thought that the building, made of thin levels of clay and chalk, was used for a single event or festival, or as a temple.

Prof Bowden added: 'The material we had to use to date the structure was scrappy bits of pottery. There are no obvious parallels for this remarkable structure in Roman Britain or, to my knowledge, elsewhere in the Roman Empire.'

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