The Thames Barrier in London, United Kingdom. This is the flood defences for the capital. On high tides and when water levels are high, the barrier raises to hold back the water level. (photo by Mike Kemp/In PIctures via Getty Images)
The Thames Barrier in London, United Kingdom. This is the flood defences for the capital. On high tides and when water levels are high, the barrier raises to hold back the water level. (photo by Mike Kemp/In PIctures via Getty Images)