Wessex Archaeology team aim to crack mystery of unidentified foundations before work begins on housing estate at the site

Foundations of a mysterious collection of medieval buildings, once an imposing complex with beautiful expensive floor and roof tiles, and substantial stone buildings set around courtyards, which vanished apparently leaving no trace of its existence 600 years ago, have been uncovered under farmland in Somerset.

The handsome floor tiles match some from nearby Glastonbury Abbey, suggesting that the site may have had religious connections. But although thousands of monastic foundations were demolished and their materials sold or scavenged for new buildings, this site appears to have been abandoned well before the dissolution of the monasteries. It is rare for one of any significance to disappear completely – this was a major complex, covering 0.4 hectares – leaving no evidence either in the landscape or in historical accounts.

Archaeologists had already found evidence of bronze age fields on the site at Longforth farm, on the outskirts of Wellington, before work starts on a new housing estate next month. There was nothing in the records to suggest anything of much importance had happened in the intervening 3,000 years, until the foundations of substantial buildings, together with the tiles, glazed ceramic roof tiles and slates began to turn up.

The team from Wessex Archaeology has only a few more weeks to crack the mystery before Bloor Homes is due to start construction work.

Bob Davis, of Wessex Archaeology, said: "This is a significant find and therefore very exciting, particularly as there are no documentary records that such a site ever existed here."

Preliminary work on dating the pottery suggests the buildings were occupied for at least 200 years, between the 12th and 14th centuries.

"At some stage however, the buildings were abandoned, the useable building materials were robbed out, and the site was forgotten," Davis added.

There is a public open day at the site on Saturday July 13, when the discoveries will be on display.

• The headline on this article was amended on 8 July 2013. An earlier version said architects were puzzled by the ruins.