It’s Barcelona, in the late 19th century, and you’re craving a glass of milk. Where do you go? Most likely you’ll head to a granja. In Catalan, the word means “farm,” but it also eventually came to refer to businesses that sold milk, typically with cows on-site. M. Viader, founded in 1870, is one of Barcelona’s oldest granjas. It’s also one of the city’s most progressive. Realizing the sanitary downsides of having cows in their increasingly urban backyard, the early owners bought a farm at the city’s edge, and created…