While there are many gorgeous waterfalls in Iceland, I think Goðafoss was my favorite. I think a lot of the reason for this was how gorgeous it was in the winter. The waterfalls in southern Iceland were beautiful, but a bit muddy around the edges as we were right on the edge of winter/spring and the temperatures were right at edge of freezing/melting. Northern Iceland was much colder, giving us this gorgeous ice and snow. (The downside of the lower temperatures was that while flying my DJI Phantom 3 Pro drone around Goðafoss, my fingers nearly froze off as my gloves were too thick to operate the remote, so I took them off. Not having thin gloves was a big mistake that I'll be sure to rectify on my next trip.)
For this shot, I used a tripod and a neutral density filter (in a holder). This blocks out much of the light, which allows a long-exposure photograph even in the bright middle of the day. This blurs the water beautifully, showing the motion of the water in a still photograph.