The Grianan of Aileach is a cool hillfort in County Donegal, Ireland, sitting a top Greenan Mountain. Built l in the 6th or 7th century, this stone ringfort is like something out of a medieval movie. It's got thick walls, terraces, and even passages inside. Legend has it that it was the seat of the Kingdom of Ailech. The place has seen its fair share of action, including being wrecked in 1101. But don't worry, it got a makeover in the late 1800s and now stands tall as a national monument and a tourist hotspot. Amazing views from here looming down onto surrounds areas.