I tried smashing it, the damn guards came. Lol
The
weakest spell that can be made with the "Open" effect will
always open doors to all town and city residences. This will also serve nicely as a fine practice spell for Mysticism.
On a related note, there is a fairly easy, low risk, way for anyone to practice their lock-picking skill. Go to any walled city and try each of the doors that lead into the walls
once. You will rarely succeed, but as long as you only try each door only once, you will not alert the guards.