Any advice on catching the train? We are staying a day after our cruise ends to explore Rotterdam and then have to get back to airport hotel in Amsterdam on a Sunday. Can we pay Euro cash for tickets? Also any must sees on such a short stay in Rotterdam? Thank you.
Just go to the station and pay cash. Rotterdam is an interesting city. Very little of the city survived WWII since the Allies tried to reduce it to a big pile of rubble and were pretty successful. The decision was made to rebuild as a new city and not an old one. A lot of very interesting modern architecture. Any good guidebook will hit the important sights.
You'll have the choice between the Intercity Direct service, taking around half an hour, and the normal Intercity train, with a change at Leiden (same platform), slightly cheaper and taking one hour. They both run 4 times per hour.