At San Luis Obispo there is a secondary nave that is the same size and at the right of the altar . This is the only `` L '' - shaped mission church in any of the California missions . The main nave is short and narrow ( as is the case with other mission churches ) , but at San Luis Obispo there is a secondary nave of almost equal size situated to the right of the altar , making this the only `` L '' - shaped mission church among all of the California missions .