A dwelling over the water.
Why would you do such a thing? For several reasons, really. First, how lovely would it be to enjoy a home situated over the water? Lulled to sleep by the lap of water against the pilings. Fresh fish and other water delicacies literally on your doorstep.
But in 500 B.C., the inhabitants of this and other crannogs had other reasons.
Perhaps safety was a reason. Crannogs typically didn't have a pier stretching to the land, and were reached only by boat. Or, if they had one, there was a substantial gap to discourage unwanted visitors such as wolves, wild boar and two-legged villains.
Actually, crannogs were a status symbol. Anyone who has spent the summer in Scotland can attest to the fact that midges are a torment to people stuck on land. So, wealthy people escaped the irritating, blood-sucking midges by building their homes on the water.
They were quite durable. Many crannogs have been found to have outlived the supporting timbers. New ones were added over the years until they simply could add no more.
And, there was, in 300 B.C., a lack of suitable building sites. Land was difficult to clear, and such was generally used to grow crops.
(an aside: there were no chickens at this time. They were brought to Scotland by the Romans)
The floors were also covered with brackens to minimize the draft beneath your feet. The tall, conical roof shed rain and snow very well. Smoke would rise, escaping through cracks in the thatch. There was no hole in the center of the roof, but doors on either side could be opened to draw the smoke if necessary.
Archaeologists have found (or found evidence of) hazelnuts, butter, cheese, smelt oats, barley, strawberries, raspberries, cloud berries, cloth, jewelry (swan-neck tunic fasteners, pins, beads and even jet--which would have come from Yorkshire), and opium poppy seeds (which indicates trade with the far east).
In one of the above photos, you will see a cloth loom. Natural coloring agents were used, such as dog's mercury, wild carrot, dock leaves and agrimony or yellow and orange; cleaverroot, strawberry, raspberry, blackberry and tormentil root for reds and pinks; blueberries to create blue, and various roots for browns.