I leave my place during the summer, it's a modern flat renovated last year with a room and a living room. It's 37 sq m, and up to 4 people can sleep there since there's a sofa bed in the living room :)
It's located between the metro station Arts-et-métiers, Strasbourg-saint-denis and République. You have access to numerous metro lines (3, 4, 5, 8, 9, 11). It's 5 minutes walk from place de la République, 10 minutes walk from Le Marais and Grands Boulevards.