These photos of Milan, taken by astronauts onboard the International Space Station, are examples of the effect seen when cities replace their older street lighting with LED lamps. In the 2012 image, the illumination level of central Milan is similar to that of its suburbs. In the 2015 image, taken after the transition to LEDs in the city’s center, the light there is noticeably brighter and bluer, further limiting the ability to see stars from within the city.
Source: International Astronomical Union. Images: NASA/ESA.