An artist put flashing red lights all around Copenhagen to measure how high up the water would rise if all the ice in Greenland melted away. Except, that wasn’t good enough:

The idea was to illustrate a prospective water level rise if the ice melts away in Greenland. Yet, somewhere along the line, he made a few incorrect calculations.
‘Technically and pedagogically it is a sound idea. The problem is that they are hanging at incorrect heights by the city lakes, where they currently sit at 11,34 metres’, said architect Ole Oerslev.
The city lakes are already 5,89 metres above sea level, so the flashing lights should have been put up at 69 centimetres height.
‘The rest of the lights put up around the city and out by the Bella Center are in the correct elevation. We wanted to display something downtown as well and even though we knew that the lights should have been at 69 centimetres, we didn’t really feel it looked like much. So we cheated a bit and decided to explain if anyone found out’, explained Galschioet.