Smelling your way around a big city can be a hazardous undertaking. In just a few steps, pleasant aromas of flowers and food can give way to car exhaust, ripe garbage and pee-soaked dog parks.

Even so, a group of brave people is sniffing their way around several global cities in order to create a series of “city smell maps.” The researchers, who come from institutions including Cambridge University and the Web company Yahoo, have so far created maps for London and Barcelona.

The results are interesting, and kind of pretty. For example, here’s a “smelly map” of London, with “emissions” smells, which the researchers describe as smells of car exhaust, gasoline and dust, marked in red and nature smells, which include flower, grass and soil, marked in green. Unsurprisingly, the auto emissions smells follow the city’s major roadways, while the nature smells are concentrated in parks and green spaces.

To see more maps, click “Know More.”