This is Casa Comalat, designed and worked on by Salvador Valeri I Pupurull between 1909 and 1911. Like a tribute to Gaudí, the building contains many elements of his architecture and is one of the most original examples of home-grown art nouveau in Barcelona: modernisme. (from http://www.barcelonaturisme.com/wv3/en/page/1155/casa-comalat.html?) Thanks to Jose for once again identifying this for me!

Another lovely window, posted earlier: