The Thames Water Tower

The Thames Water Tower mystifies people driving around Shepherds Bush Roundabout, with good reason. First and foremost, it hasn't worked for some time. Even when it did, most people did not realise that it was a giant barometer (covering up a bit of huuuuge pipework for the London Water Ring Main). It used to contain blue water which would rise with high atmospheric pressure (indicating good weather). I hope they get it working again, it was quite fun to be one of the few who knew where the world's biggest barometer was.