Very very real. You can go there and see it. You can walk around and sit where people sat over 5000 years ago.
I grew up not far from there (it's about a six or seven hour drive, followed by a two hour ferry journey, so it's not something you do every day, but barely 160 miles in a straight line) and it was all Iron Age brochs and such. Skara Brae was already ancient and lost when they were built.
But why did they put so many spinner traps and magic mouths in the perfectly rectilinear, monster-filled maze underneath the town?
In all seriousness, I had no idea until just now that Skara Brae was a real place, and not just a setting for tales sung by bards.