Ciutat Vella is, as its name suggests, the oldest part of Barcelona. It includes buildings and attractions from all the city history and has the most important monuments.
Ciutat Vella is divided in four quarters:
Barceloneta or Little Barcelona was built after King Felipe V ordered the construction of a new fortress in order to control and punish the city of Barcelona, that fought against him during the war of Spanish Succession.
Barri Gòtic is the oldest part of the old town. Fully pedestrian, this area is quite popular for visitors to see the history of the city. While not as active in boutique shops as La Ribera next door, it boasts its fair share of night life and shops. Most people walk through here to view the quite stunning architecture with the ancient building leaning this way and that on their centuries-old foundations. It is also the location of the Barcelona Cathedral which is a focal point of the city.
La Ribera is a large section of the old town that encompasses everything between Arc de Triomf and Via Laietana.Regardless of whether you go to the upper or lower sections, it is a very happening neighborhood with lots to do an see. By day, there are many small shops and local designers. By night, there is a thriving bar and restaurant scene. It's easily reachable on foot and contains no end of old buildings, many of which date back to the 15th century.
El Raval is the neighborhood of the old town just to the west of Las Ramblas. It's a vibrant place for nightlife and while still very much an immigrant neighborhood, it's home to no end of bars and restaurants. While not as historically significant as say, Barri Gòtic or La Ribera, but gradually more civic structures are sprouting in the area, such as the Filmoteca.