Named for the legendary king (you know, the one who pulled the sword from the stone?), Arthur's Seat is a dormant volcano sitting atop the city of Edinburgh. While the Scottish capital has plenty to offer any traveller in their 20s — from charming castles to "the birthplace of Harry Potter" — hiking Arthur's Seat is among the loveliest, most exhausting ways to spend your afternoon in this city. If not for the view from the top, than for the sense of sheer accomplishment.