The legends about a sunken building in the middle of Lake Valgjärv were ripe already in the 15th century. In 1489, Siegbert, a monk from Riga, recorded a story told of a manor that lies under the placid water of the White Lake (valge - white in Estonian), sunk by heavy rains the night after its lord married his own sister.

It is believed that the first ever dive in Estonia was organized on the lake in 1640 by a local nobleman Wolfgang Heinrich von Anrep, to check if the legends of an underwater manor were true.

And they were.

Nevertheless, the sunken structure was not properly studied until 1958, when professional archaeologists first inspected the site.

It was established that the wooden remains were those of a pile-dwelling - a house raised on piles over the surface of the lake - connected to the shore by a bridge. Up to 9-meter long logs and other building material were found where the house once stood. The structure was dated to the second half of the first millennium.

Remains of a building in Lake Valgjärv (Photo: Indrek Ostrat/National Heritage Board)

Several smaller expeditions have since taken place and now, Kalle Virtanen, a PhD student from Finland, is surveying the site with the help remote sensing specialists from the University of Zagreb, Croatia.

The Croatian team have named their GPS-controlled remote sensing device Platypus, Maaleht reports. Platybus, with its special cameras, will document the structure and give archaeologists a detailed view of it. The results of the survey, however, won't be published for another year.

Virtanen first became interested in Lake Valgjärv nearly two decades ago, for the unique ancient structure in the lake is unparalleled even in Finland, the land of a thousand lakes, he said.

There are, however, a dozen comparable pile-dwelling sites known from North Latvia, in Lakes Āraiši and Ušuru among them.

"Like many fields, archaeology too is becoming increasingly international and by example of Lake Valgjärv, we can say that this is very beneficial," Virtanen told Maaleht. The Finns especially have been very interested in Valgjärv and made a documentary about it, which aired in YLE years ago but has never been screened in Estonia, local paper Valgamaa reports.

"We are mostly interested in understanding what drove the ancient settlers to build such an intriguing house in the middle of the lake," Virtanen told the paper.