To add a bit more detail: the amount you have to zoom in for shapes to look right will increase with absolute latitude. So the equator pretty much always looks good on Mercator, Europe looks good if you're looking at the continent scale, but then in Greenland and Antarctica you'll need to be zoomed in to a regional or city-size, or even closer in. So when it's really important to get a broad-scale view near the poles, map makers will switch to something like a polar stereographic projection or similar. (I've personally just used a transverse mercator projection (whatever UTM zone is most convenient) when doing data analysis near the poles.)
