There have been some questions about how to take a day trip to
Take the Metro to Estacio de Sants. Follow the signs from the Metro stop to the bus station. You will have to cross a busy street, but the bus station is not far.
It is probably wise to book at least a day ahead. The first time we went, there were no tickets left on the bus that day. However, they sold us tickets for the bus that left the next day. You will need to show your passports. Tickets are issued with your name on them and for specific buses.
We took the 8:15 am bus to Andorra la Vella. The bus was modern and had a restroom. The trip took 3 hours and was an enjoyable ride through spectacular scenery on modern roads.
The principal industry of Andorra appears to be tax free shopping. We had a very nice meal there, then took the 3:15 pm bus back to Barcelona. Again it took 3 hours. Buses leaving at 6:15, 8:15, and 10:15 are also possible although you will miss seeing the scenery in the winter. We did not have to show our passports at the border although the customs officers looked around the bus before we re-entered Spain.
The round trip fare was 44.50 Euros, and the bus left precisely on time.