And I thought seeing Mont Blanc from my town Le Creusot, France (a 216 km line of sight) was very long... not! Apparently it would only rank 6th from the bottom of this list!
Edit: this is awesome, I managed to use http://www.udeuschle.selfhost.pro to simulate the view of Mont Blanc from my city: its exactly 215.2 km away: http://www.udeuschle.selfhost.pro/panoramas/panqueryfull.asp...
And as it turns out this is not the max line of sight, there is the hypothetically visible Grandes Jorasses slightly to the left (221.5 km away). You have to use the 10x zoom to see it: http://www.udeuschle.selfhost.pro/panoramas/panqueryfull.asp...
http://www.udeuschle.selfhost.pro/panoramas/panqueryfull.asp...