A 2-storey magic shoppe. The proprietor lives and experiments upstairs and sells their wares downstairs. In truth this can be any large shop that offers a wide range of precious things. It could even by a one-room museum, with artefacts (forged and real) on display on the ground floor.
Depending on the amount of magic in your campaign, the hemisphere of sigils at both the entrance and the main desk on the ground floor, could have magical effects that prevent thieves from leaving the premises with unpaid items unless the shopkeeper verbally wishes them well on their way.
There's a secret cubby behind a cupboard in the storeroom for very rare items and upstairs the proprietor has a rather large and well stocked vault.
Use the three-quarter shots if you want to show more of the walls to the players, or instead rely on the close up inserts to show more detail while on the map. (I intend to make these player accessible journal images in Foundry so that anyone in the group can take a look at whatever they like).
More than just a shop
My intention would be treat it at first as just another magic shop for the players to spend their gold, then get them involved in the plight of the shop owner, perhaps become allies or even friends, be invited up for dinner... all over a series of sessions, so that the location and (access to it) grows as their relationship blossoms with the NPC. Perhaps even affording them a place to stay, research weird artefacts and perhaps help the shop thrive with whatever the heroes delve from forgotten catacombs.
Made in Dungeon Alchemist, with photoshop post effects. The .dam files are available at the $10 tier.
100px/grid
40x20 map size