Thingvellir is also of essential historical resonance for Icelanders. Viking clans chose the valley as the spot for an annual assembly beginning in the year 930, forming the world's first parliament. Almost no physical trace remains of those gatherings. Iceland quietly leaves it to the visitor's imagination to people the valley with merchants and charlatans and men declaiming from the Logberg, the "Law Rock." In a tourist-intensive age, it is an idiosyncratically modest choice, and more satisfying in the end than reconstructing Viking huts and paying actors to wear horned helmets.
In a way, a plunge into Silfra is way for a tourist to shed his life of ease for a couple of cold hours and fancy himself as tough and fearless as the figures in Njal's Saga, the tale of ancient Icelandic blood feuds.
Not that the Vikings went snorkeling. In fact, Kotze said, Silfra had a much less appealing use a millennium ago — as a Viking toilet.
There were clashes at the annual assembly and because Silfra is narrow and depressed, the Vikings "went down there to do their business" with peace of mind.
If You Go...
SILFRA, ICELAND: Several outfitters including DIVE.IS — http://www.dive.is — offer snorkeling and diving trips to Silfra, about a 45-minute drive from Iceland's capital, Reykjavik. Prices for snorkeling are around 15,000 kronur ($120) and for diving about 35,000 ($273). The prices include transportation from Reykjavik, but divers who want to save a little money or spend a few extra hours exploring Thingvellir can get to the park on scheduled buses during summer. Dry suits and gear are included, but participants should bring thermal underwear and warm socks. Hot drinks and cookies are provided afterward, but the easily chilled may want to bring along a sandwich or other food to refuel their internal furnace. The trips can be expanded into full-day excursions that include time to explore Thingvellir and visit the renowned Gullfoss waterfall and Geysir thermal field.