Le Château de Vincennes is a former fortress and royal residence and is one of the few remaining medieval castles in France. It was a preferred residence for French Kings from the 14th to 16th centuries. The donjon or Keep was built in the 14th century and is the largest in France. Restoration of the Keep began after WWI and it was given landmark status in 1913.
Above: inside The Keep. The room on the upper left displays photos of some of the famous prisoners who were held at Vincennes which include Nicolas Fouquet, the royal minister of finance of Louis XIV (September 1661) (see Château de Vaux-le-Vicomte).
The Sainte-Chapelle de Vincennes sits within the fortifications of the Château de Vincennes and is no longer used as a church. It is a Gothic royal chapel that was inspired by the royal chapel Sainte-Chapelle, Palais de la Cité in Paris but only has one level apposed to two. Below: views from The Keep, Château de Vincennes.
Vincennes is the last stop on Metro line 1; exit, cross the street and you are there! There is a fee to enter. Your ticket will be checked at various locations such as the Sainte-Chapelle de Vincennes. There are restaurants in the area. Metro Line 1, Vincennes.