Aarberg is a historic town and a municipality in the Seeland administrative district in the canton of Bern in Switzerland. Aarberg lies 20 kilometers from Bern above the river Aare. With an area of , Aarberg borders Bargen, Kappelen, Lyss, Radelfingen and Seedorf. Aarberg is not to be confused with Aarburg in Aargau or with Aarbergen in Germany. The town was once located on an island with the Aare and Little Aare (Kleine Aare) flowing around it. The old town grew up around the edge of the island with a large open plaza in the middle. In addition to the old town, Aarberg also includes the new outer quarter, and the villages of Spins, Mühletal and Grafenmoos. The official language of Aarberg is (the Swiss variety of Standard) German, but the main spoken language is the local variant of the Alemannic Swiss German dialect. Where Aarberg now stands was once an island surrounded by the Aare and the Little Aare. By 1138 there was a small pilgrim home and hospital with a bridge, the Bargenbrügg, over the Aare. This bridge was a key river crossing from Bern to Büren an der Aare. The town itself was founded between 1220 and 1225 by count Ulrich III of Neuchâtel. The count had recently acquired the rulership over this region and needed a central location from which to rule. The island and the key bridge was a natural location for a town. Aarberg is first mentioned in 1236 as Arberc. In 1267 it was mentioned as de Arberch. By the 14th century, Aarberg lay along the most important of the three trade roads in the region. The old Roman roads that connected Solothurn, Aarberg and Murten as well as southern Germany with Lyon and Rome all passed near Aarberg. The oldest official seal of citizenship in the town dates from 1249. Ulrich IV reaffirmed the town privileges in 1271. Initially the town was unwalled with two rows of wooden houses around a central narrow plaza. Following fires in 1419 and 1477 the town was rebuilt in stone and set back about creating the current, impressive central lens shaped plaza.