Things I can do on a 3 day layover in Reykjavik

I am contemplating this on the way back from a trip to Europe, the stopover would be in mid June, but it seems expensive and I'm not sure what to do! Convince me!
  1. The "golden circle"!
    Not shower, not even really a circle
  2. Þingvellir National Park
    I've never been but someday: home of the eldest democratic institution dating to Viking days in the 900s You can scout it out for us!
  3. Go for a swim & have ice-cream afterwards!
    The ultimate Icelander experience 😊 here is a list I made: TOP PLACES TO VISIT IN ICELAND
  4. hunt
    Suggested by   @brent_test_account