Giant Crossword of Lviv

Though a crossword puzzle with 19 squares across and 34 squares high might seem daunting enough, perhaps it might appear more challenging if the physical puzzle stands over 100 feet (30 m) tall.

Located on the side of an apartment complex in Lviv, Ukraine, the world's largest crossword puzzle -- in physical size, at least -- is an interactive art work aimed at bolstering critical thinking and urban exploration.

Similar to a scavenger hunt, around 80 clues to the crossword puzzle are scattered throughout the city's major landmarks. Visitors must explore popular attractions, such as historic monuments, museums or parks, before they're able to solve the building's brainteaser.

To further tantalize visitors, the answers are displayed in fluorescent lettering that can only be viewed when lit up at night. Each nightfall, tourists can be seen crosschecking their results outside the towerblock.