Marstrand Island is only accessible by ferry, but it's a fast, cheap ride. There are no cars allowed on Marstrand, which means biking is the way to go!
You can bike around the entire island, through forests and onto epic seaside slickrocks. There are also several trails crisscrossing the island to make for alternative routes and bailouts.
The slickrock on the side facing out to the open ocean is incredibly fun to ride! It's similar to Moab, but only with an ocean as a backdrop. Look around, explore, and you're guaranteed to find some interesting lines!
When you're done riding, check out the mighty, historic Carlsten Fortress in the centre of the island (you can't miss it) and grab a bite to eat at one of the historic restaurants in town.