Stone age burial mounds (tumulus you would call one; plural would be tumuli? tumuluses?) for Celtic royalty in ancient Ireland and other parts can be pretty impressive. The one Owen and Fetch pass through is rougher than some you might find where the walls are lined with brick and passages wind deep under the hill. I don’t know if any of them have murals, but I thought it might be worth giving the reader an idea what the Tuatha Dé Danann might have looked like. They’re usually depicted as more glamorous than you see here, but they’re in a hurry. Who has time to do one’s hair when being chased by hordes of Milesians. (Forebears to modern humans in Ireland, it is said.)