The length of the Gotthard Base Tunnel, the world’s longest and deepest traffic tunnel, running beneath the Swiss Alps, providing a high-speed railway link between northern and southern Europe.
The $12bn link, which opened in 2016 after two decades of work, was considered so important it originally went to a referendum of Swiss voters, who backed it largely because of its environmental promise of removing a million trucks a year from the roads.
In places the tunnel is 2.3km beneath the surface at a depth where rock temperatures reach 46C. Speaking of rock, some 28 million tons of it was excavated, in no less than 73 different varieties. The drilling machines responsible were more than 400 metres long and the amount of concrete used – 4,000,000 cubic metres – could have built the Empire State Building 84 times.
Length of each one of three massive canals being dug in northern China to alleviate critical water shortages. The region contains 50% of the country’s population, but only 20% of its water. The South-North Transfer Project will take 48 years to complete and will tap into several rivers – though principally the Yangtze – to supply 44 billion cubic metres of water per annum. Mao Zedong first had the idea back in 1952. By 2014 the bill was already up to $79 billion not only making it one of the most expensive engineering projects the world has ever seen but raising the prospect that the water it delivered could actually end up being too expensive for the average Chinese consumer to use.