Casa de la Cultura is one of Quito's central cultural institutions, a broad complex of museums, galleries, theatres, and public spaces near Parque El Ejido. The circular modernist building is hard to miss, and the programming gives a useful window into Ecuadorian art and public culture beyond the colonial centre.
It is worth checking what is open before you go, as exhibitions and access can vary. When the galleries are active, this is a good counterweight to Quito's churches and plazas: less polished for tourists, but closer to the country's living cultural conversation.