Tons of fantasy stories and historical documents use the term “league” as a unit of measurement and I honestly had no real conception of how far a league was until I decided to use it in one of my 10 10 Minute Plays and needed to look it up:
League (unit) – Wikipedia, the free encyclopedia: A league is a unit of length or area long common in Europe and Latin America, although no longer an official unit in any nation. The league most frequently expresses the distance a person, or a horse, can walk in 1 hour of time (usually about 3.5 miles or 5.5 kilometres).
So it is distance measured by time. I like that.