In April I visited Norway and since I didn't have a lot of time and most of the tourist sites were still closed, I did the Norway In A Nutshell Tour (to be booked at almost every trainstation and tourist office). You first take a regular train, and form there you take a special train (it has to descend into a steep valley) up to Flam where you take boat trip a along the Aurlandsfjord and into the Naeroyfjord which is truly beautiful: high fjords, very green water, high waterfalls, it was just perfect! You will have a busride and a trainride back, so it's a pretty long day, and a bit touristy, but it's a great way to see something of the fjords in a fast way. You can also take this trip from Bergen, so you can include Bryggen on your trip and see 2 UWHS in one day.