Golden Circle and Secret Lagoon on a Luxury SUV. This tour takes you to three exceptional sights in Iceland: Thingvellir National Park, Geysir geothermal area and Gullfoss waterfall. This day tour offers you a chance to see and experience some of Iceland’s nature, geology and history. Secret Lagoon is a natural hot spring, located in the small village of Fludir. It is the oldest swimming pool in Iceland made in 1891. and its water holds at 38-40 Celsius (100-104 Fahrenheit) all year. It has magical surroundings with a small geyser erupting on the side.