Ask anyone who has never been to Barcelona before anything about the city, and you usually have a maximum of 3 replies - FC Barcelona, something about Gaudi or Las Ramblas. Indeed many tourists always want to be close to the city's most famous street, despite knowing about the noise levels and petty crime that can often give the Ramblas such a bad name (more often than not blown out of proportion by certain travel forums).
Les Rambles in Catalan, is actually a collection of boulevards/promenades all seamlessley joined to form the plural "ramblas". The old Roman walls of Barcino like many a Roman town, were flanked on one side by a river. This dry river bed is what is now today Las Ramblas. Any trip to Barcelona is incomplete without strolling up and down Las Ramblas, and I would say a Sunday is the best day.
Rambla de Canaletes is the first stretch, named after the fountains at Plaça Catalunya - if you drink from the fountains, legend has it that you will one day return to Barcelona (and more than likley have a funny tummy for a few days, too). Here pensioners huddle to put the world to rights and celebrations for any Barça games overflow here from the Plaça.
Subject of much discussion for the tardis-style animal seller stands is the next Rambla de los estudios - more than likely making refernece to the nearby library on Carrer Hostpital. The lizards, rabbits and birds provide a bit of entertainment for the kids and at night get folded up like an origami duck into the smallest possible space that passers by don't even notice that this was the same place they passed earlier. I'm not animal rights activist, and it might be warm and cosy as far as I know but it must be a bit squashed, right?!
Rambla de Sant Josep is so called after La Boqueria market, which not everyone knows is called Saint Joseph's market. This also has the great Mirò floor plaque just at the entrance of Carrer Hospital/Sant Pau. This is where the main stretch of cafes appear and the Liceu Opera house, giving it's name to "rambla de los capuxinos" which speaks for itself.
Finally we have Rambla Santa Monica, which is where all the artisits collect. There are the usual charicature artisits, Chinese artists who write your name in script or colourful representations of letters, etc. but there are also some amazing portrait artists (the guy who works only with brushes in black and white is AMAZING!) and some great ethnic art, too. They store their work in the communal store room down on Arc del Teatre (readers of shadow of the wind, that's where the bookshop is!) and I remember once out on a night out, and seeing some of the guys setting up at around 4am! They told me that if they didn't start at that time, they didn't have enough space.
If you're thinking of coming to sample the sights that las ramblas has to offer, then try a self catering apartment for rent in Barcelona , instead of a hotel option. Also, see this Barcelona Guide.