A breath of fresh air in a crowded city could come from devices that provide the environmental benefits of a small forest in areas where space is extremely limited. It’s called the ‘CityTree’ - a freestanding vertical unit that is covered in moss and lichens, with a huge surface area to absorb harmful pollutants, nitrogen dioxide and ozone. The creators from the company Green City Solutions explain that each of these CityTrees has the environmental benefits of 275 trees, but takes up 99% less space and can be installed for only 5% of the cost of planting trees.