The bus eases out of Reykjavík before dawn, headlights cutting across low clouds as the first steam plumes from geothermal vents appear like sentries along the road. Over three days you skim the spine of South Iceland: a raw mosaic of black sand, basalt cliffs, thunderous falls and the slow, blue muscle of glaciers. On Day 1 the landscape opens—Thingvellir's rift valley lays the tectonic boundary under your feet, Strokkur punctuates the air with boiling water, and Gullfoss drops in two thunderous stages. By Day 2 the coast takes over, Skógafoss and Seljalandsfoss roaring near volcano-shadowed slopes; you lace up crampons for a guided blue-ice walk on Sólheimajökull. Day 3 answers with the surreal calm of Jökulsárlón: bergs the size of houses drifting toward a black-sand shore called Diamond Beach, glittering like cut glass.