L ydia Ourahmane has been living in Venice this year, in an apartment on the Giudecca with gorgeous views over the lapping, flickering water to the main Venetian island. The British-Algerian artist has been making an exhibition that will open to coincide with the Venice Biennale , the art world’s biggest global gathering. For months, artists and curators from every corner of the planet have been shipping and installing thousands of artworks on the little archipelago. Then, in November, when it’s all over, they will disperse again. There is something both amazing and dreadful about this vast circulation of stuff . This is not, however, what Ourahmane, 33, has been doing. Instead, it is from Venice itself that her show has sprung. Itinerant by habit – she lives in Barcelona and Algiers, and spent her childhood “ping-ponging” between the UK and north Africa – she is a conceptual artist, in the proper sense, an artist of ideas.…