Venice is masked by sheets of snow. The emergency services negotiate choppy waters to deal with daily hazards as well as life-and-death emergencies. There's a sunken boat to rescue, an elderly lady with a suspected stroke and, in this city built on wood, the most dreaded call of all - fire. We see how Venice deals with thousands of tonnes of rubbish, turning it into power which is fed back into the city. Venice may be over 1,000 years old, but staying afloat requires 21st-century innovation.