If you haven't I recommend on your first day you should go see the Sagrada familia Church.
It will mesmerized you .Casa Batllo and La Pedrera two very impressive architectural gems
For lunch I suggest eating at El Nacional for the best in local foods
Wandering the most famous street in Barcelona is a must .I love walking up and down the Rambla
enjoying the side cafes ...Guys you will agree with me that Barcelona has the best soccer team on the planet
