If you turn north off the Ring Road onto Route 998 just west of Jökulsárlón, you'll inevitably find your way to the visitor center/parking lot that serves as the trail-head for the Svartifoss Loop. This will be your starting point for a 4 km round-trip trek that starts out at a quad-burning incline and eventually levels off into an relatively flat, easy push towards another of Iceland's beautiful, popular waterfalls.
If you're expecting the grandeur of a Gulfoss, or even a Seljalandsfoss, we'll spare you the disappointment here. However, what Svartifoss (the Black Waterfall) lacks in awe-inspiring intensity it more than makes up for in sheer scenic beauty. First of all, your initial ascent, which is itself dotted with smaller waterfalls, will open up incredible views overlooking Southern Iceland and the North Atlantic coast in the distance. Then there's the cascade itself, a 24 meter deluge pouring over those well-defined columns of basalt for which this island is so renowned. Sound intriguing yet? If your up to the task, you can even venture off the path on the eastern side of Svartifoss and wind your way to the top of the falls, but be advised that the going can be tricky and you do so at your own risk. All in all, even if you just stay on the well-worn route, it's a beautiful sight, and will likely only take about two hours out of your day. We'd call that a worthwhile investment.