Raufarholshellir Lava Tunnel

Raufarholshellir Lava Tunnel is a guided cave tour through a lava tube about 1,000 years old in the Threngsli area of South Iceland, on Route 39 near Hveragerdi and roughly 30 km (30-35 minutes) south-east of Reykjavik. The tube formed during the eruption that produced the Leitahraun lava flow, when the outer surface of a river of lava cooled and hardened while molten rock continued to flow beneath, leaving a hollow passage. Visitors walk through a section of the tunnel on lit walkways and see colourful mineral deposits, lava stalactites and smooth, rippled walls, with guides explaining the geology and how the tunnel formed. The tour lasts about one hour and is rated easy: there is no technical skill requirement and the route involves only modest walking, although the ground is uneven in places and some sections have low ceilings. Helmets are provided, while visitors bring warm clothing and sturdy shoes because the cave stays cool all year. The operator runs the tunnel as a managed attraction with a safety briefing, marked paths and lighting, and guides lead groups through the passage and know the nearest exits in case anyone needs to leave early. Age limits and group sizes are set by the operator, so families should confirm the minimum age before booking. Prices run roughly ISK 7,000-10,000 per adult. The tunnel is a stable environment, so tours operate in every season; conditions to avoid are mainly severe weather on the road to the site, as winter storms can make Route 39 and the access track difficult. Visitors should stay on the marked walkways and avoid touching the formations, which are fragile and take a long time to form. The tunnel is close to Hveragerdi, a town known for its geothermal greenhouses and hot springs, and to the Reykjanes and Golden Circle routes, which makes it an easy add-on to a day trip from the capital. Mobile phone reception is limited inside the cave, so photos are best taken with a camera or a phone with a good low-light mode.