4. Space for chemical waste. «It is a huge scandal that there is no place for chemical waste in Greece, which produces around 200,000 metric tons of industrial waste a year. Where does it go? A small amount goes abroad, the rest into the Asopos and other rivers and into the sea,» said Kaliambakos. Such an installation could be created underground in some old mines which have very deep tunnels of impermeable rock. 5. Roads and public transport networks. Roads cover a large percentage of land in cities. Rivers of asphalt and automobiles cover open spaces and divide the residential and social fabric. The overall solution is to decisively reduce the use of private vehicles. Putting transport underground can also help. To start with, we can promote underground rail transport, like the metro. But some cities are already trying out putting entire road grids below ground, so as to free up surface space. The classic example is the Big Dig in Boston, USA, where they buried 10 of 16 lanes (after digging up 12.5 million cubic meters of earth) in the center of the city in order to revitalize it. Aren’t such plans extraordinarily expensive? «Let’s calculate the cost of the land that we will reacquire,» answered Kaliambakos, noting the possibility of new planning that takes social needs into account. From that point of view, the NTUA researchers are in favor of putting the Proastiakos suburban railroad below ground because it threatens to partition entire districts of Athens (such as Aghioi Anargyroi and Sepolia).