Venice’s government has voted to build mobile barriers for the city’s lagoon to protect the city from flooding. The barriers “will consist of 78 hollow, hinged steel flaps, each 18-28 metres high and 20 metres wide, at the three entrances from the sea into the lagoon. In normal conditions they will lie on the sea bed, but when there is the threat of a tide higher than 110 cm above mean sea level, air will force water out of the flaps, which then rise up to hold back the water. The €6 billion (£4.1 billion; $6.4 billion) project, which is expected to be completed by 2011 (to put this cost in proportion: the road works in the centre of Boston have cost $14.6 billion).”