Thingvellir National Park is where the Althing, an open-air assembly representing all of Iceland, met from 930 to 1798. It's like the OG parliament, where they made laws and settled disputes in a cool outdoor setting. The park includes remains of the Althing, like turf and stone booths, and even some buried 10th-century stuff. Plus, there are traces of old-school farming from the 18th and 19th centuries. Basically, it's a thousand-year-old time capsule of Icelandic history and nature vibes.