The only place on earth you can swim between two tectonic plates, the North American and Eurasian plates, a metre apart, with…The only place on earth you can swim between two tectonic plates, the North American and Eurasian plates, a metre apart, with your hands on each. Visibility over 100m in glacial meltwater filtered through lava for decades, it is like flying. Neon-green 'troll hair' algae in the Cathedral section. The fissure opened in a 1789 earthquake and is fed by Langjökull glacier meltwater that spends 30-100 years percolating through porous lava, which is why it is chemically pure and impossibly clear. Þingvellir is also where Iceland's parliament was founded in 930 AD, a UNESCO site. Anchorage: Inland lake, no boat access; a road-accessible stop for a superyacht itinerary out of Reykjavík. Hazards: No site-specific hazards noted, brief normally. Plus