Château de Brest, Military fortress in Brest, France.

Château de Brest is a fortress on a rocky spur at the mouth of the Penfeld, built of rough dark grey and tan masonry. A tall rounded defensive wall with a lighter parapet encloses a long rectangular building with a dark slate roof and small dormer windows. A round stone tower with a flat roof and thin mast stands to the right.

Roman forces established the initial fortification in the third century to defend against maritime threats. The site was repeatedly expanded and reinforced over the centuries to keep pace with changing military needs.

The castle houses the National Maritime Museum with collections of naval equipment and scientific instruments that document French seafaring traditions. The exhibits show how closely this fortress's story connects with the French fleet.

Visitors can take guided tours throughout the year, with expanded summer programs and educational activities designed specifically for children. The site is well-accessible and guides help explain the different areas of the fortress and how it functioned.

The castle is the oldest in the world still in use, and it has kept its military role since the Roman castellum. A museum of the Navy has occupied part of the site since 1958, housed in the new maritime prefecture built in the courtyard after the wartime barracks were destroyed.