The apartment was exactly what we hoped for after reading the post and seeing the images - very stylish, small but cozy, very clean and practical for our purposes, complete with small kitchen, small bathing tub and TV. Of course there was wireless internet and a comfy bed, as well as lots of closet space to store all of our things, and a nice coffee maker.
The location could not be more central - within a few steps you could reach several bars and cafés (if you're a light sleeper, use earplugs in the weekend - the Spanish like to party!).
Any interesting location in the center can easily be reached by foot - the Thyssen museum is only 3 minutes away!
A walk to the beach takes about 20 minutes.

All in all, it was a really pleasant experience and Cristina and Raul were very friendly, helpful, laid-back hosts who sent us tons of useful tips fpr the city. Recommended!