Architecture rewards a different way of working. Straight lines, window grids and roof edges give you structure to build along, so instead of hunting by colour you follow a cornice or a row of balconies across the board. Busy street scenes are among the easiest large puzzles you can pick — there is so much incident that almost no two pieces look alike.
Follow the architecture rather than the colour. A cornice, a row of balconies or a line of windows gives you a track to build along, and it is faster than sorting by shade because you can see it on a single piece. Watch for repeating window grids on modern buildings — those are the one place a city picture turns genuinely hard, because two pieces really can be interchangeable.
Difficulty: Easy to medium. Repeating window grids can be deceptively tricky. Every picture here is graded automatically by how much its neighbouring pixels differ, rather than by subject — why that is the thing that matters.
Pick any picture below, choose anywhere from 12 to 2000 pieces, and play free in your browser. Share one link to solve it with friends on the same table, or use a photograph of your own instead. Browse every category.