If you are a one day Barcelona visitor, youd better not to try seeing as much as you can but to examine the most significant places of Catalan capital during your superfast Barcelona day tour. The first must-see place is Sagrada Familia church in Carrer de Mallorca. To visit it you should buy a ticket, it is better to get in it in the morning because at this time there are less people. On getting your ticket, look at it carefully and find the hours of visitation, e.g. from 10 to 11.
After the excursion over, go by underground to Liceu Station and have your dinner at La Palmera Restaurant because its cuisine is really good and not too expensive. Dont want to go there? Just enter any other Barcelona restaurant all of them are good enough.
After dinner you may have a walk along Las Ramblas and the Gothic Quarter (Watch your purses, bags, cams and other valuables!). Every their stone is a piece of history.
If you are lucky to enter the lower storey of Caelum, a shop selling sweets, you will see ancient Jewish womens bathhouse (The lower storey is open since 5 pm). The shops address: Calle Palla, 8.
If you cross Vía Laietana, you will be able to see and visit Palau de la Música Catalana (Palace of Catalan Music) and wonderful Santa Maria del Mar church. The Gothic Quarter is full of bars and restaurants serving local food, so, you will be able to try a lot of tasty things.