Our longest day trip in Iceland was to see icebergs in Jokulsarlon Glacier Lagoon. Despite the very long day (the excursion was about 18 hours!) the trip to Glacier Lagoon was absolutely worth it. Most tour companies offer this as a 2-day trip, but a few now have a 1-day option. Aside from the glaciers and incredible icebergs, we also saw some epic waterfalls, and were lucky enough to spot the Northern Lights on the bus ride back to Reyjkavik.