The Forestiere Underground Gardens in Frenso are over 100 years old. The trees grow in wells connected by shallow tunnels. It does look more like a Tatooine underground house than a garden, but still neat. It's open for tours in normal times:

http://www.undergroundgardens.com/

Unless you want to grow plants that fare better in colder climates. Just cover them over in the middle of summer and make sure they have some sort of cool air flow through the trenches.