house. >> they say it is actually 11,000 years old. and it's something that could give us insight into how our ancestors lived. the bbc's jenny hill reports. >> reporter: carved by stone age man. it's 11,000 years since someone built this timber decking. this, it's thought, the earliest evidence of carpentry in europe. in 8500 b.c., this entire valley would have been under water. but there's plenty of evidence that human beings settled around its edges. it's that evidence which makes archaeologists say this site is as significant as stonehenge. >> there's two in that section. >> reporter: every hour here they turn up a new discovery. they've only excavated a tiny fraction of the site. but every arrowhead, flint, and bone fragment is a vital clue about the people who live here. >> let's be honest, they were probably very much like you and me. they would have looked very much