Caen is the birth place of William the Conqueror, and as such as an interesting past. It is also a pretty cosmopolitan place in comparison to most places in La Manche! It is a short drive away from Ouistream port, one of the main arrival points for ferries from the UK.
It was very badly damaged during the bombing of the WWII, and on the outskirts there is the vast Memorial Museum, which would certainly fill a rainy day. It has many films and displays that explain in good detail the whole of the war.
A few of the things to see in Caen, would include the Abbaye d’Homme et Abbaye de Femmes, the ruins of the Chateau, which includes a gallery of modern art with a fairly large print making section.
Caen also has a very good market on Sunday mornings at the Port de Plaisance in the centre of Caen.