Drag the slider back to 500 BC and only the Mediterranean rim is lit. By 100 AD the Roman frontier along the Rhine and Danube has appeared; the Baltic fills in after 1000; the Scandinavian and Russian capitals arrive last.
“Founded” is slippery. Many cities have a traditional date (Rome 753 BC, Venice 421), a first written mention (Berlin 1237, Moscow 1147), or archaeology showing people there much earlier (Athens, Lisbon, Edinburgh). The date used is the conventional one for continuous urban settlement; each city’s blurb notes the wrinkle.