The Castrum Rauracense in Kaiseraugst and the Bürkli

17 May 2026

It is hard to imagine today, but the villages of Augst (Canton Basel-Landschaft) and Kaiseraugst (Canton Aargau) formed the largest conglomerate in present-day Switzerland during Roman times.

At the time, the two other major cities were Aventicum (Avenches) and Colonia Iulia Equestris (Nyon) in the present-day canton of Vaud.

Augst and Kaiseraugst formed the Roman Colonia Augusta Raurica, named after the Celtic tribe of the Rauraci and Emperor Augustus. Basel’s Ratshaus houses a statue of its founder, Lucius Munatius Plancus (87-15 BC).

Lucius Munatius Plancus, the founder of Augusta Raurica but not of Basel!)

Augusta Raurica was situated on the Rhine and was a significant city on the Roman border (Limes) with the Germanic tribes in the third century. Around 300 AD, the Romans constructed the largest fortress in Switzerland, known as the Castrum Rauracense. The castle is also considered an internationally significant heritage from the late Roman period.

The western gate in Roman times and today

Its dimensions are 292 by 155 metres, indicating this border town’s importance in the defence line. The castle probably also had an administrative function. In any case, the nearby museum Augusta Raurica shows daily (rich) Roman life. Among other things, the museum houses the Kaiseraugster Silberschatz.

At the time, a smaller fort stood on the other side of the Rhine and the other side of the Bridge, the remains of which can also be seen today.

Some of the castle’s walls in Kaiseraugst remain, providing an impression of the complex’s size. Archaeologists have also managed to make a reasonably reliable reconstruction. However, after more than 1,700 years, the walls need major maintenance to repair the effects of frost, precipitation, and wind.

The Bürkli near Möhlin-Riburg

In the 4th century AD, a watchtower belonging to the late Roman border fortifications (Limes) probably stood on the Bürkli; in the early Middle Ages, a large fortification stood here.

The Bürkli, a reconstruction of the early medieval castle complex comprising the outer bailey, the outer ward and the inner bailey. Photo: Aargau Cantonal Archaeology, René Kindlimann

The Bürkli near Möhlin-Riburg occupies a steep-sided gravel terrace between the Rhine and the Möhlinerbach. The late Roman Limes along the Rhine, stretching from Kembs in Alsace to Constance on Lake Constance, was secured by forts and watchtowers. In the hinterland, forts guarded key transport junctions.

The Bishop of Augusta Raurica

One of Switzerland’s oldest bishop’s seats is also in Kaiseraugst on the banks of the Rhine. This site is also open to the public.

St. Gallus church, 5th century