Thiepval and Tyne Cot are very moving and really bring home the enormity of the number of casualties during WW1, especially Thiepval when you realise all the names there are of men whose bodies were never found. The whole area around the Somme is dotted with WW1 cemeteries, some very small.

As has already been mentioned Monte Cassino is definitely worth a visit. You really need a tour guide there to appreciate the whole battle - we had a good one and we never would have realised the whole story without him. My father was with the Eighth Army there but he never talked about it. After he died I found a poem that he had written about it (A lament for Liri plain) which brings tears to my eyes every time I read it.