Nice airport... I love it.
Picturesque old harbor, which dates to 1913. Some good restaurants here, plus the maritime museum and whale watching, bird (Puffin) and Northern Lights tours. Lovely to just look out across the bay at the snowy mountains. One of the harbor’s newer attractions (2011) is Harpa, Reykjavik’s glimmering, glass concert hall. It’s home to the Icelandic Opera and Iceland Symphony Orchestra; a conference hall is attached. If you want to stay in the harbor, Icelandair’s Hotel Reykjavik Marina is a great choice.
One of my very last moment before heading for the BSI for my bus to the airport was coming to the waterfront, all my luggage in tow and light rain falling upon my face. From the Harpa Concert Hall to the hills along the horizon, it's a great spot to catch some fresh air (because, you know, there's none of that in Iceland) and an expansive view.