Route 1 circles the entire island — glaciers, waterfalls, black-sand beaches, and geothermal fields, returning to Reykjavik after roughly 1,300 km with no backtracking required.
Loop start and end — most people drive it clockwise to hit the south coast waterfalls first.
Reynisfjara's black-sand beach and basalt columns, plus two of Iceland's biggest waterfalls just before town.
Jökulsárlón glacier lagoon is the detour just before — icebergs drifting out to sea.
The "capital of the north," near Goðafoss waterfall and Lake Mývatn's geothermal fields.
The western leg back closes the loop — Snæfellsnes peninsula is a worthwhile last detour if you have an extra day.