After leaving Barcelona, my partner and I want to spend three days somewhere between Barcelona and Valencia. We think we want to stay in a coast town but know the weather will be hard to predict in early October. It will be mostly "down time" but we'd like to take some day trips (by bus or train) as well. Any suggestions for a good town to stay in and places we can explore on day trips?
We spent a couple of weeks in Sitges and really enjoyed it. It's not very far from Barcelona, however. We visited Tarragona on a day trip.
Tarragona would be the main city to visit in between. There are some smaller beach towns, and Sitges is the most prominent. Tarragona is the oldest Roman town in Iberia and has some excellent ruins and scenic sea views. It can fill a day or two, but that's about it.
As Janet and Douglas mention, both places are worth visiting. Sitges is a small (30000 inhabitants) coastal town located 40km south from Barcelona, which can be reachable by commuting train (http://infocatalonia.eu/w/ibDWG) and Tarragona is the old capital of the Western province of the Roman empire (http://infocatalonia.eu/w/IltXs) and it preserves many of the Roman features of a capital: a circus -one of the biggest in the empire-, an amphitheatrer, an aqueduct, a forum and the walls of the city (http://bit.ly/tarracoruins). Not too far, the Monastery of Poblet i Santes Creus (http://infocatalonia.eu/w/tvPGY) a Cistercian abbey, founded in 1151, located at the feet of the Prades Mountains. The austere, majestic monastery, which has a fortified royal residence and contains the pantheon of the kings of Catalonia and Aragon. A bit further south, still in Catalonia, you have the medieval city of Tortosa (http://infocatalonia.eu/w/2SqVV) which preserves significant examples of medieval, Renaissance, baroque and modernist architecture. And in the area you can visit the wetlands of the Natural Park of the Ebre river (http://infocatalonia.eu/w/tIvor), nearly 8000 hectares of one of the most important natural reserves in the South of Europe. These are only a few things you can do but depending on your particular interests there are plenty more.