About 95 km south of Barcelona, also on the coast, lies the pleasant city of Tarragona. After leaving our car in a parking garage, we tried to find our way to the Roman remains without a map. This wasn't easy, as the city is spread out along the coastline. Fortunately, the woman at the train station who had sold out all of her maps pointed us in the right direction: most of the sights are in the north, in the upper town. We walked up there, in the midday heat.
The Tourist Information in this part of town holds very Spanish opening hours (closed between 1 and 5 p.m. or so), so we just had to follow our own instincts. The enormous city walls can't be overlooked though. From there we roamed the narrow streets of the charming old town. Most of the Roman remains are only fragments. The amphitheatre is quite complete, but I've seen better ones. It was closed too, for unclear reasons. Not part of the WHS but worth a mention: the cathedral of Tarragona, also in the upper town, is just great.
On our way back to Barcelona (via the A7 toll road) we had a glimpse of the Roman aqueduct. If you're in the mood, there's a small parking lot on both sides of the road from where you can have a good look and take pictures. We'd had enough however after another satisfying day. Advice for future travellers to Tarragona: bring your own map and take your time!