Shoppers in Manningtree were on the look-out for Dr Who after seeing what at first looked like a giant Dalek.
But the 8ft square glistening object on the town's market place on Saturday morning turned out to be a mirrored camera obscura.
It was created by staff and residents of Mistley's Acorn Village, the Clacton Road home for adults with learning difficulties.
Woodwork instructor Richard King and about 18 residents built the obscura, which will be displayed at an exhibition in Great Dunmow next weekend and will feature in science lessons in primary schools in the area.
Mr King said obscuras dated back several hundred years and there were various versions but Acorn's was based on a Victorian model.
"People go inside and it gives a magical image of the surrounding landscape. It's like standing inside a pinhole camera and the children in particular love it," said Mr King.
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