Hafnarfjörður has plenty of accommodations (all listed at www.hafnarfjordur.is) -- the town's sales pitch is that it's nice to be close to but outside of the "big city" -- but peaceful lodgings can be found just as easily in Reykjavík.
Note: This information was accurate when it was published, but can change without notice. Please be sure to confirm all rates and details directly with the companies in question before planning your trip.
