Half eaten kebabs, a broken high heel, a puddle of sick in a shop doorway - typical remnants of a Saturday night out in the city. The European Monitoring Centre for Drugs and Drug Addiction (EMCDDA) though, measure a much less visible indicator of a city's partying habits. Every year, they analyse waste water samples around the continent for traces of illicit drugs such as cocaine and MDMA.
Looking at traces of cocaine found at the weekend, renowned party town Amsterdam is at the top of the scale with 1,028mg of the drug per one thousand people flowing through the drains. In second is Swiss banking hub Zurich with 976mg and rounding off the top three is the Danish capital, Copenhagen, with 780mg.