def phy_grid_dims(conn):
    """ Returns physical grid dimensions. """
    cur = conn.cursor()
    cur.execute("SELECT grid_x FROM phy_tile ORDER BY grid_x DESC LIMIT 1;")
    x_max = cur.fetchone()[0]
    cur.execute("SELECT grid_y FROM phy_tile ORDER BY grid_y DESC LIMIT 1;")
    y_max = cur.fetchone()[0]

    return x_max + 1, y_max + 1