Puzzle Building

In past we have seen puzzles on clothes, now we have here a puzzle on the wall of a building. It's the newest tourist attraction in the city Lvov, Ukraine. This artistic projectis placed on 30 meters tall wall of a multi-stored residential house.Although its blank during the day-light and at night when speciallights are switched on the puzzle, it become visible. Questions forthis crossword are scattered in different parts of the city, such asmonuments, theaters, fountains etc. So while touring the city, you cananswer the questions and at night, check the accuracy of your answers!