They are a familiar sight on the streets and sandy beach of Barcelona: vendors, blankets spread out in front of them, selling copies of branded shoes, handbags and football shirts to frequently disinterested passers-by. Now Catalonia and the Balearic Islands have chosen Top Manta, a Barcelona-based cooperative representing the mostly migrant, undocumented sellers, as inspiration for its entry to the Venice Biennale on architecture, which opened last weekend.