The Stone Age equivalent of a cathedral has been unearthed in Orkney, the largest structure of its kind found in Britain.

It dates to the Neolithic period (7000-1700BC) and was found not far beneath the surface of the narrow strip of land that divides Harray Loch from Stenness Loch on the Orkney mainland.

It is an area that is at the heart of Orkney's World Heritage Site which boasts extraordinary archaeological richness. The building has been found between two of of the most famous standing stones sites in the world, the Ring O' Brodgar and the Standing Stones O' Stenness.

But the archaeologists working on the site said yesterday that this latest find was unprecedented, and that the vast structure is as awe-inspiring today as it would have been in theStone Age.

At 65ft long, and similarly wide, it would have dominated the landscape, dwarfing the Ring O' Brodgar (the 27 standing stones range from 7ft to over 15ft) and even the Stenness Stones (the four standing rise to 19ft).

"In effect it is a Neolithic cathedral for the whole of the north of Scotland," said Nick Card, from the Orkney Research Centre for Archaeology, who is leading the dig at the Ness of Brodgar.

The shape and size of the building are clearly visible today, with the walls still standing to a height of more than 3ft.

Far taller when built, they are 16ft thick and surround a cross-shaped inner sanctum where the 40-strong excavation team have found examples of art and furniture created from stone.

The building was surrounded by a paved outer passage. Archaeologists say this could have formed a labyrinth that would have led people through darkness to the chamber at the heart of the building.

The team has also discovered that a standing stone split by a hole shaped like an hourglass was incorporated into the structure, something never seen before in buildings from the period.

"A building of this scale and complexity was here to amaze - to create a sense of awe in the people who saw this place," said Mr Card.

"The perfection of the stone work is beautiful to look at. This is architecture on a monumental scale and the result is the largest structure of its kind anywhere in the north of Britain."

The building may have served as some kind of temple, perhaps playing an important role on the journey from life to death in the beliefs of the people of the time.

"Today it is still so impressive and when you look down on it from above it is almost jaw dropping," he added. "It is a real privilege to work here and we feel that this was a very special place when built four-and-a-half to five thousand years ago."

Dr Colin Richards, reader in archaeology at Manchester University and a leading expert on the period, said the building would have stood at the heart of Neolithic Orkney.

"A structure of this nature would have been renowned right across the north of Scotland, and is unprecedented anywhere in Britain," he added.