Poznan Old Market Square is known for its colourful old tenement houses, which occupy the central part of the square and surround it. In the past, they were the headquarters of rich merchants who sold their goods in the lower parts of their houses. Each tenement house was painted in a different colour to mark the property of a given merchant.
More about this image here: https://sumfinity.com/hdr-photos/poland/poznan/old-market-square/
