Spectacular waterfall Aldeyjarfoss, 41km south of Goðafoss, is well worth the journey. The Skjálfandafljót river churns through a narrow passage and into a deep pool in a canyon lined with intriguing basalt column formations.
Take unsealed Rte 842 to the northern entrance/exit of the long, lonely 4WD Sprengisandur route (Rte F26) across the interior highlands. Note: only 4WD permitted on F26, which is the last 3.5km to Aldeyjarfoss' small parking area, as you drive south.
You can park your 2WD near the gate for F26 and walk the 3.5km if you don't have a 4WD.