Simplify the following text for a Grade 9 native English-speaking person.
Original: The Mission church of San Luis Obispo is unusual in its design in that its combination of belfry and vestibule is found nowhere else among the California missions .
Simplified: Mission San Luis Obispo deTolosa is one of the first missions founded in California . The mission building has an unusual design , with both belfry and vestibule , that canâ t be found on other missions .