⚠️ Why Public Bus Doesn't Work
The Golden Circle is a loop — public buses are hub-and-spoke
Strætó buses run hub-and-spoke from Reykjavík. The Golden Circle requires a circular route (Þingvellir → Geysir → Gullfoss → back). No public bus does this loop in one day.
Buses to Selfoss/Flúðir run 1–2× daily. You'd spend 80% of your day waiting at rural stops. Missing one connection = overnight stay.
Public buses stop at towns (Selfoss, Laugarvatn), not at the actual attractions (Þingvellir visitor centre, Geysir, Gullfoss waterfall). You'd need taxis from stops anyway.