Metro line 1, 5 or 8 to Bastille, come out at the July Column in the middle of the square. Also bus 20, 29, 69, 76, 86, 87, 91, and Vélib' stations all around. This is a self-guided tour: no group, no guide waiting. Start whenever you like. Many shops close Saturday, open Sunday.
Next to, the Opera and th Louvre