A free browser extension that puts a city's real outline (from OpenStreetMap) on Google Maps and lets you drag it anywhere. It keeps its true size: the outline grows towards the poles and shrinks towards the equator, exactly as Mercator distorts areas. See area, population and density, rotate the shape, or draw your own area with a lasso. Moscow is 25x Paris; Berlin fits Paris 8.5 times. Nothing is tracked, no account. Firefox now, Chrome Web Store soon. Great for geography lessons.