The Castle of the Teutonic Order is the architectural focal point on the island and a splendid setting for various occasions. It is the heart of the island and where the Bernadotte family lives.

The Schlosscafé and some parts of the castle are open to the public for refreshments, exhibitions and events.

The Castle of the Teutonic Order was designed by Johann Caspar Bagnato and built under his supervision (1739 – 1746).
Despite limited finances, he created an architecturally well-balanced, symmetrical harmonious castle. The arms of the two wings open out in the shape of a horse-shoe towards the mainland; whilst the back of the building faces the lake. Two stories rise up from the base. The splendid coat of arms of the Grand Master Clemens August of Bavaria, district commander Philipp of Froberg and the Mainau commander Friedrich of Baden adorn the west gable. The coat of arms of the Teutonic Order adorns the east gable facing the lake.
 Bagnato didn’t build an impressive stairwell as seen in Würzburg Castle; instead he designed simple elegant staircases in the wings which lead to the upper floors.

The ‘White Hall’, formerly the audience hall, is the heart of the castle and painted in white and gold. Its appearance as we know it today dates back to 1883. The hall is only open to the public for concerts or very special events. The Heraldic Hall, a central room in the basement of the former Corps de Logis, is open to the public for various exhibitions. The Schlosscafé leading into the Palm House is open all year round.

The architecture of the buildings forms a fantastic harmonious ensemble – they are a unique example of baroque in Southern Germany.