Þingvellir, a rift valley bounded by cliffs to the east and west, about 6km (3 3/4 miles) apart, is the symbolic heart of the Icelandic nation, though it's hardly clear why at first glance. The first Icelandic parliament (or Altþing) convened here in 930, and remained here off and on through 1798. (The Altþing, now in Reykjavík, is widely considered the oldest continuously-operating parliamentary institution in the world; it was actually disbanded for many years by Iceland's colonial rulers, so the Isle of Man has its own claim to this streak.) Þingvellir's annual parliamentary meetings were hardly limited to legislative sessions and court proceedings, however. They were also a news conference, trade fair, singles event, poetry reading, and circus ring all rolled into one. To Icelanders, Þingvellir is not only where their political independence originated, but also where their oral and literary traditions were passed on, and where their very sense of peoplehood formed. In the 19th and early-20th centuries, Þingvellir became a potent symbol and meeting place for the growing nationalist movement for independence from Denmark. In 1930, marking the millennium of the first Altþing, Þingvellir became Iceland's first national park. When Iceland gained formal independence in 1944, 20,000 people -- one-sixth of the country's population -- gathered at Þingvellir. The proclamation of independence was read in the pouring rain, followed by 2 minutes of silence, and then the peal of church bells. In 2004 Þingvellir became a UNESCO World Heritage site. It's still used for national commemorations. Note: The tourist industry will tell you that the land to the west is "North America," tectonically speaking, and the land to the east is "Europe" or "Eurasia;" but the land to the east can't really be called Eurasia, because there's another major rift line farther east, running from Hella and Hvolsvöllur in the south to Mývatn in the north.
Þingvallavatn, the largest natural lake in Iceland, forms Þingvellir's southern boundary; 90% of its water comes from underground springs and fissures. Þingvellir sits directly on the continental rift: Land west of the Almannagjá (Everyman's Gorge) is moving west, and land east of the Hrafnagjá (Raven Gorge) is moving east. These borders have moved about 70m (230 ft.) apart in the last 10,000 years and continue to separate at about 8mm (1/3 in.) per year. The broad, lava-covered plain in the middle has fallen about 40m (131 ft.) in the same time span, forming the cliffs on either side. (In other words, 10,000 years ago the top of Almannagjá was level with what is now the valley floor.) In 1789, after an earthquake, the valley floor fell 5 feet in 10 days. The entire plain is riven with small crevices from all this geological stretching.
South of Þingvellir -- Near the southwest shore of lake Þingvallavatn are the Nesjavellir power plant and the Hengill hiking area, which is also accessible from Hveragerði to the south. The brochure Hiking Trails in the Hengill Area can be found at Nesjavellir.
The word "geyser" derives from this fascinating geothermal area full of hot springs, steaming creeks, mud marbled in mineral colors, turquoise pools encrusted with silica, and one reliable geyser. Access is always open.
Geysir (GAY-seer), discovered and named in 1294, refers to both this general area and a specific geyser, which once spouted as high as 80m (262 ft.), but is now just a calm, steamy vent with occasional hisses and gurgles. Rocks and soap were often dumped into Geysir to make it erupt on demand, only accelerating its demise. Recent research has shown that if the water level were lowered 2m (6 1/2 ft.), Geysir would again erupt every 30 to 60 minutes to a height of 8 to 10m (26-33 ft.). Thankfully Strokkur (The Churn), another geyser a few meters (about 10 ft.) from Geysir, spouts reliably every 5 minutes or so. Each spout varies in size, so wait to see at least two or three.
The geyser mechanism is not completely understood, but scientists agree that the eruptions are basically caused by a pressure buildup formed when hot water and gas is trapped beneath a cooler layer of water. Strokkur's eruptions reach as high as 35m (115 ft.). (Americans can be seen affecting nonchalance, since Old Faithful reaches 25-55m/82-180 ft., and Steamboat reaches 90-120m/295-394 ft.) The spouting water is around 257°F (125°C), so be careful not to stand downwind. Geysir is no doubt a natural wonder, but leaving Strokkur aside, there are several other Icelandic geothermal fields of equal or greater interest. Some may even find it anticlimactic, as if they had traveled to Sandwich just to eat a sandwich.
Along the Hvitá river, just 7km (4 miles) from Geysir, Gullfoss is Iceland's most iconic and visited waterfall, as elegant as it is massive. Gullfoss means "Golden Falls," the probable source of "Golden Circle." The waterfall is a 5-minute walk from the parking area, and you'll hear it well before you see it. Two smaller falls at the top lead to an L-shaped curtain cascade dropping another 21m (69 ft.) into a 2.5km-long (1 1/2-mile) gorge. The viewing angle doesn't quite let you see where the water hits bottom, but the spray (bring a raincoat) would conceal it anyway. When it's sunny, you can always expect a rainbow; in winter the falls are filigreed in beautiful ice formations.
Near the falls is a monument to Sigríður Tómasdóttir, who probably saved Gullfoss from being submerged by a hydroelectric dam in the 1920s. The daughter of the farmer who owned the property, Sigríður threatened to throw herself over the falls if the project went through. The courts ruled against her, but the hydroelectric company gave in to public pressure, and the contract simply expired in 1928.
The visitor center (Mon-Fri 9am-6pm; Sat-Sun 9-7pm) is right next to a cafe and gift shop (Oct-Apr daily 8am-6pm; May-Sept 8am to as late as 10pm).
Note: This information was accurate when it was published, but can change without notice. Please be sure to confirm all rates and details directly with the companies in question before planning your trip.