Château d'Ambérieux-en-Dombes, Medieval fortress in Ambérieux-en-Dombes, France.

Château d'Ambérieux-en-Dombes is a ruined fortress whose square Romanesque keep rises 19 metres, built of carrons, clay bricks fired to shades from black to pink. Its walls consist of two brick skins one metre apart, filled with lime and pebbles. Three towers remain, two square and one small circular tower that served as a prison, along with traces of a chapel.

The fortress was built between 1370 and 1376 under Humbert V de Thoire-Villars as part of regional defense strategies. It proved its military strength when it withstood an assault by Savoyard troops in 1460.

The castle was the seat of the seigneurie of Ambérieux and the head of a châtellenie of the principality of Dombes. Local tradition holds that it was a favourite residence of the first Burgundian kings and perhaps the site of a palace of Gondebaud. The village church was built in the 19th century in the middle of the castle, replacing the Romanesque chapel whose stones it reused.

Access to the fortress is gained from the local road, and visitors can explore the outer areas and view the architecture from different angles. The flat terrain surrounding the structure allows easy walking and provides clear views of the tower design and overall layout.

The castle walls are built of carrons, clay bricks moulded in spring, dried until autumn and then fired; those nearest the fire turned black, the others pink, which explains the colour variation visible on the brickwork. The walls consist of an inner and an outer leaf one metre apart, the gap filled with lime and pebbles.