if you have time in Flåm during your Norway in a Nutshell Tour (or you are lucky enough to stay overnight), and are up for a pleasant walk through the valley, the Old Flåm Church (aka Flåm kirke aka Flåm kyrkje) makes for a great (if slightly long) stroll and visit.
getting there starting facing the train tracks, catch the main road to the left (in front of the white hotel) and follow it 3.6 km (nearly 2.25 miles, for those of us who are metric-challenged) to the church which will be on your right. it felt like i was walking forever since there were no signs indicating progress — it took me (at a very quick clip) 35 minutes to get there. there is a sign in Flåm that says a round trip will take 1.5 hours, and someone at Tourist Info said that really is the speed of Norwegian speedwalkers, so set aside 2 hours. i think i did pretty well, then! even with stopping to really explore the small church, it took me about an hour and a half total, but your time will vary if you’re not walking up a sweat like i did.
sidebar i extended my stay in Flåm to be about 3 hours total when i booked my Norway in a Nutshell because i had heard there are things to do around town. this gave me plenty of time to eat (luckily no line at the cafeteria) and head down to the church, but judge timing for yourself based on what you want to see and your walking speed. another bonus: the later Flåmsbana train to Myrdal was effectively empty, easily less than 10 passengers total, so i had half a car to myself — meaning i had open windows on both sides. btw, if you don’t have this much time but want to visit, you can rent a bike in Flåm — just note that the church asks you to not bring the bike into the courtyard.