Tour description provided by Viator

Go cave exploring and snorkeling in one incredible day on this day trip from Reykjavik. Visit Iceland's Gjábakkahellir cave and the Silfra fissure, both located in the UNESCO World Heritage-listed Þingvellir National Park. Alongside your guide, discover the depths of some of Iceland's most stunning natural wonders as you explore a mysterious cave and snorkel in a pristine, dream-like underground pool.

Visit Thingvellir National Park, a UNESCO World Heritage site, for a day of spelunking and snorkeling during this eco-adventure from Reykjavik. On this full-day tour from Reykjavik, accompanied by your certfied guide, you will get the chance to visit the hidden underworld of a typical Icelandic lava tube cave for some caving exploration as well as the phenonmenal fissure of Silfra where you will get the chance to snorkel between the tectonic plates of America and Eurasia.  Explore some of Iceland's most spectacular natural wonders in just one day on this full-day adventure tour. Following pickup at your Reykjavik hotel, climb aboard a comfortable, climate-controlled minbus for the 60-minute journey to the UNESCO World Heritage-listed Thingvellir National Park. Upon arrival, listen to a short safety lecture and introduction to the area. Get fitted for spelunking and snorkel gear, then follow your guide to your first adventure.  Explore the lava fields under the park itself by visiting a typical Icelandic lava tube cave. View and climb through a lava cave, located in one of the most active volcanic areas in the world. During the 1.5-hour tour of the cave, admire shield volcanoes, products of lava flows that left spectacular layers of rock and lava deposits over the years.  Please note: In the winter, you will explore Leidarendi cave. Break for lunch (own expense) before continuing on to visit Silfra. During the summer you will visit Gjabakkahellir cave. At the Silfra fissure, slip on your snorkeling gear and explore the otherworldly underground pool. Drift between the tectonic plates that separate North America and Eurasia, following your guide to the most scenic places in the pool.  After a day of exploring the spectacular underground wonders in Thingvellir National Park, head back to Reykjavik for drop-off at your hotel.Please note: During the winter this tour will take you to Leidarendi lava cave but during the summer Gjabakkahellir will be explored.