Lauri Vanhala wanted to figure out the best place to buy an apartment in Helsinki, so he built an interactive sort-of-isochrone map of the city. He explains: “I calculated the travel time from every address to every other address in Helsinki around 7:30-8:00am (about 30 billion searches total!). Then I calculated the (weighted) average travel time to anywhere in the city, using amount of jobs in the target area as weight.” [OSM]