We flew WOW to Europe with a 19-hour stop in Iceland. We left San Francisco about 8 pm, landed in Iceland about 10 am the next morning drove around a little, got a bite to eat, went to bed at about 9 pm, and got up at 3:30 to catch the flight to Paris. 
Looks like you should have spent more time in Iceland!!
Yeah, but the cheap-flight deal was a for a layover of only 19 hours.
Super cool layover.