A glacier hike is hands down a MUST do activity while in Iceland. You cannot access glaciers without a guide or proper equipment so I suggest going for a small group tour with Arctic Adventures. The meeting point is in Skaftafell National Park. They will drive you in their super jeeps to the base of an outlet glacier of Vatnajökull, the biggest glacier in Europe, and gear you up for an epic adventure of hiking on a glacier.
It's not crazy strenuous, a walk might be more accurate but hiking sounds cooler!
GLACIER XTREME - GLACIER HIKING & ICE CLIMBING TOUR
Age Limit: 14 years old
Time: 6 hours
Level: Challenging
GLACIER EXPLORER - MODERATE GLACIER HIKE IN SKAFTAFELL
Age Limit: 14 years old
Time: 5-6 hours
Level: Moderate
GLACIER WONDERS - EASY GLACIER HIKE IN SKAFTAFELL
Age Limit: 8 years old
Time: 4 hours
Level: Easy