The botanical garden associated with the former convent is famous for its collection of Oaxacan plants. We haven't yet paid the hefty entrance fee and have only had glimpses of it from the museum.
This picture is from the inside of the church of Santo Domingo de Guzman. The light is poor and I include this fuzzy, overworked photo to encourage you to google the church and find some good pictures of the inside.
The yucca in the garden near dusk.