Architect Eric Clough secretly built an insane scavenger hunt into a Park Avenue apartment he renovated. It took the family months to discover the scavenger hunt and weeks after that to figure it all out.

Via thevine.com.au:

“In any case, the finale involved, in part, removing decorative door knockers from two hallway panels, which fit together to make a crank, which in turn opened hidden panels in a credenza in the dining room, which displayed multiple keys and keyholes, which, when the correct ones were used, yielded drawers containing acrylic letters and a table-size cloth imprinted with the beginnings of a crossword puzzle, the answers to which led to one of the rectangular panels in the tiny den, which concealed a chamfered magnetic cube, which could be used to open the 24 remaining panels, revealing, in large type, the poem written by Mr. Klinsky.” Whew!