The village you're passing through is actually called Trøym, though everyone calls it Hemsedal. It's been the centre of this valley since the municipality split from Gol in 1897.
The wooden church on the north side of the road dates from 1882. It replaced a medieval stave church that stood here for over 600 years. When archaeologists excavated the old church site in 1963, they found traces of an even older building underneath - possibly from before the stave church was built. The site is marked at the old cemetery at Kyrkjebøen if you want to find it.
The valley's name comes from the river Hemsil, which runs through to Gol. The Norwegian word "hems" - that small sleeping loft you find in old cabins - actually comes from this valley.