Guess the Castle shows one photograph a day — a castle, fortress or palace drawn from the 500 most famous on Earth. You have six guesses, and every miss answers with the distance and compass direction from your guess to the answer, because every guess is a real castle on the world castle map.
A new castle arrives at midnight. Yesterday’s answer — and all 2,400 landmarks — live on the atlas, each with its photo, founding century and story, built entirely from open data.