Air pollution is a health risk to millions of people in Europe. An indicator for air quality is the concentration of particles with a size of ~10 micrometers (PM10). Heavier pollution occurs in densely populated or industrial areas where we can observe more combustion of fossil fuels. The COVID-19 pandemic made many citizens remain at home when Europe went into lockdown in early 2020. Such a sudden decline in demand for transport and industrial production is assumed to have a positive impact on air quality in many regions. \nYou can inspect the magnitude of this effect using annual PM10 concentration maps. \nTo explore the pre-COVID air quality, select e.g. the year 2019. Note the general spatial patterns: Coastal and rural areas tend to have higher air quality than continental, urban areas. One may further observe a gradient from North/West to South/East, with hotspots in northern Italy, southern Poland, the Balkan region and Turkey. \nTurn on the 'Compare' tool and select the year 2020. By dragging the divider left or right you can visually compare the two years. Looking at Europe as a whole, you may notice a slight decrease in 2020's air quality, as more green pixels tend to turn yellow or orange than vice versa. This may be unexpected, as 2020 was shaped by lockdowns and other COVID containment measures. However, air quality depends on various anthropogenic and natural factors. For example large-scale weather patterns and terrain play a crucial role in the composition of atmospheric gases.\nYet, the expected air quality improvements are in the data! You can adjust the scale and zoom to a region of interest. Many urban areas, which had COVID restrictions in place and experienced a sudden drop in human activity in 2020, also show lower PM10 concentrations in that year. Turn off the 'Compare' tool and 'Activate regions to analyze'. Now click on a major city in northern, western, or central Europe, for example Stockholm (Sweden), Paris (France), or Dublin (Ireland).