Hvalfjordur is a wide fjord in the west of the country which makes you do a very big detour if you are heading north in the direction of Snaefellsnes Peninsula.
There is now an underground tunnel that crosses Hvalfjordur leaving you near Akranes and allows you to drive straight on. I must say that I took this tunnel in the beginning because it saves you a lot of time and 45 km of curves in the fjords! I recently decided to drive the long way around. And I didn't regret it. The view of the fjord, between the sea and mountains, is wonderful and the landscape is spectacular.
At the bottom of the fjord it is possible to stop for a hike to visit the beautiful Glymur waterfall, the highest waterfall in the country but there's a little bit of a walk to get there, which makes it less popular!