Raufarhólshellir

A 1,360-metre lava tunnel formed by an eruption 5,200 years ago, and one of the easiest caving experiences in Iceland — it's only 30 minutes' drive from Reykjavík. The standard guided tour (about 6,990 ISK, 1 hour) follows a lit boardwalk through the main tunnel. The adventure tour goes further in and involves scrambling through tighter sections.

The tunnel walls show clear flow marks from the original lava river, and in winter, ice formations build up near the entrance — stalactites and stalagmites that catch the light well. The temperature inside is around 2-4°C year-round, so dress warmly even in summer. Helmets are provided.

Raufarhólshellir is on Route 39 near Þorlákshöfn, about 35 km from Reykjavík. It makes a good half-day activity, especially if you're combining it with a south coast drive or a Blue Lagoon visit. Tours run year-round. Book online at thelavatunnel.is — walk-ins are possible but not guaranteed.