When travelling I realized how bad my estimation of distances was in unknown places, so I created this tool one afternoon to help me compare a size of an unknown place or city to something I know.
It turns out people are much better at relative comparisons than absolute comparisons.
The comparison doesn't work well for places with too big latitude differences (e.g. Greenland vs. Australia). This is because Google maps use Mercator projection that preserves angles (so that streets in Norway meet at right angles) but not areas.