St. Pauli is one of the most famous Red-light districts throughout Europe and nightlife centre of Hamburg, Germany. Every year this single square mile attracts more than 20 million visitors. Thus, it is common to see drunken revellers, especially foreigners, urinating on the street. Tired of tourists urinating on walls, neighbours and owners of commercial property in the area have decided to strike back.
To solve the problem of nocturnal revellers who urinate on the walls of their neighborhood, the locals had the idea, paint the walls with a hydrophobic paint. That has the ability to redirect the urine directly to the feet of "owner." To prevent them, residents also installed warning sign that says, "Do not pee here! We pee back."
However, the cost of this solution is very high, 116$ needed for one square meter.