I really enjoy the puzzles in the game and would love to see more. Maybe a tower of different puzzles that may be solved for prizes? If all puzzles are completed, a badge may even be rewarded.
I remember fondly the puzzles in Krokotopia and Mount Olympus/Atlantea, and thought Tajniak/Jawniak were really cool. Those are a nice break from the usual defeat, collect, defeat & collect, etc.
Maybe not just one tower that's all puzzles, but a puzzle-rich area of the spiral like Krok was, full of logic puzzles, memory puzzles, powers of observation puzzles, reaction time speed tests, stuff like that mixed together.