Geohashing is a method for finding an effectively random location nearby and visiting it: a Spontaneous Adventure Generator. Every day, the algorithm generates a new set of coordinates for each 1°×1° latitude/longitude zone (known as a graticule) in the world. The coordinates can be anywhere -- in the forest, in a city, on a mountain, or even in the middle of a lake! Everyone in a given region gets the same set of coordinates relative to their graticule.
"Spontaneous Adventure Generator!" That sums up the appeal of this little game for me! It's the same thing I find appealing in planning out 60+ weekend rides. Trying new trails, plotting new routes. ADVENTURE!
Denver is geographically unfortunate because it is what is called a "split city," meaning that an intersection of graticules, those 1x1 longitude/latitude grids, falls almost directly in the middle of the city, and so we recognize four of them in our area: NE, SE, NW, SW.
Which means that our field of play grows from about 3,381 square miles (69 miles to a degree of latitude by approximately 49 miles to a degree of longitude at 45 degrees form the equator) to four times that at 13,524 square miles.
Which is a friggin lot.
The city and county of Denver is ~155 square miles.
So there's almost a 1/50 chance that it will fall within 10 miles of Denver.
Which all goes to say that in these parts, if a hashsite happens to be a reasonable distance from you, it's a shame not to go after it.
Like I did on Hallowe'en Eve.
According to the tool at chemical-ecology.net the four-graticules sized grid is 138.09353334000397 miles by 107.31667373389479 miles long, or 14819.738662209928518 miles square. My original estimate was off by about a thousand miles. I'll now assert confidently, when asked, that our playing field is about 14,819.75 square miles.