For a 9-day trip, I recommend 2 days in London, visiting the Tate, then to Amsterdam for a day by boat (to Hoek van Holland), taking the train to Paris for 2 days and ending your summer in Barcelona.
For a 9-day trip, I recommend 2 days in London, visiting the Tate, then to Amsterdam for a day by boat (to Hoek van Holland), taking the train to Paris for 2 days and ending your summer in Barcelona.