All across northern Scotland, you can still see the skeletal remains of prehistoric skyscrapers. Unique to Scotland, these enigmatic Iron Age towers are called brochs. 2,500 years ago, these drystone structures dominated the Highlands and Islands, yet so much of their story remains shrouded in mystery. Join Tristan Hughes as he ventures across northern Scotland to investigate these extraordinary ancient buildings, seeing some spectacular scenery along the way: from the western Highlands to Orkney.