A topic I've thought is "A Magical City" - create an isolated city, that generates all its needs from raw vis and local resources around it, with no need to import anything from the outside world (including, notably, mundane society). It's surprisingly difficult, as there are just too many things that people need/want. The nearest I've come up with is something like the following:
Gormenghast: The City That Is a Dream
Gormenghast is an eight-magi strong covenant located in a low-level Magical regio in the Ardennes mountains. Extremely isolationist, it subsists solely on products it manufactures locally from its raw vis sources. It is famous for its huge number of covenfolk, which are arranged in strict guilds and classes. Notable practices and enchantments include:
The Pits: A series of pits enchanted with ReHe and ReAn designed to hold food indefinitely. Gormenghast relies on ritual spells using An and He raw vis obtained from the magical woods surrounding it to fill these with a small selection of crops and meat, which constitute the bulk of the covenfolk's diet. The covenant's magi must learn and master these rituals, which they cast annually.
Adjacent to the Pits are further warehouses, holding a few other raw ingredients including salt, steel, wood, and marble. These are similarly produced magically. In addition, a few small gardens within the city produce various spices and herbs.
The compact with the forest and mountains spirits that grant the covenant its vis prohibits the covenant from taking from the forest and mountain; it instead guards these Magical places, receiving raw vis in return.
All in all, the covenant maintains a stock of 8 or more goods created magically with Momentary Creo Ritual spells, that need be cast annually or nearly so, from He, An, and Te raw vis. That's not a small amount of rituals to cast every year, in addition to the Aegis! And yet it still leaves the covenant poorly-stocked, with only a scant few raw ingredients to work with.
The Craft Tools: A series of enchanted craft tools, each allowing the wielder to employ Rego Craft magic with his Finesse score. The tools are handed down within the guilds of Gormenghast, and new tools are occasionally created and rewarded to the guilds.
Using these tools allows the covenfolk to somewhat-circumvent the poor selection of raw materials, as intermediate materials that would normally be required to craft things aren't needed using Rego Craft magic. They also significantly boost the productivity of the covenant's roster of artisans, as each can produce a day's work "in an instant", so that even with some Limited Use on the items each artisan can produce many times over his mundane counterpart. A result of using these tools is that most artisans in Gormenghast are "generalists", focusing on increasing their Finesse and getting to know finished-products and ideas in a wide-range of areas rather than increasing any actual Craft scores. The guilds are still limited to the Forms each toolset works with (Animal, Herbam, and Terram being the most common). In addition to these main guilds, the guild of Scribes, which specialize in crafting and copying books, is also a power in Gormenghast, and unlike the others its members typically study their Crafts (Scribing, Bookbinding, Illustration, as well as a smattering of Magic Theory, Latin, and Artes Liberales) as foiling a magus' book through bad dice rolling is not desirable.
Poseidon's Gift: An arcane connection secretly draws water from a nearby lake to the covenant's great fountain, from where it is distributed to the rest of the city.
This is crucial as creating water from raw vis is not feasible, IMO. You need too-large cisterns. So I think summoning them from afar is the only other good possibility. Excluding dumb-luck of having a large-enough fountain/river on-hand, which is cheating.
The Faerie Market: Despite forbidding trade, a secretive faerie market exists in Gormenghast, which only a few can enter, and they too perhaps unwittingly. This market allows trade in all manner of goods that are not available to Gormenghast covenfolk, from exotic meals to holy books. It is rumored that despite their protestations and public attempts to locate and stomp the market, the magi actually participate in it in disguise.