A couple if weeks back while on holiday in France, I persuaded the wife that a visit to the World War 2 German submarine pens at Saint-Nazaire would be a great day out ( for me anyhow).
It is also the site of the famous Saint-Nazaire raid by the British to put out of action one of the only atlantic dry docks capable of servicing the largest of the German battleships.
The view from inside one of the pens, the entrance would originally have had doors.
This panoramic view is taken from the top of the entrance to the basin.