Street of Cunning Artificers
From Discworld & Terry Pratchett Wiki
This street in Ankh-Morpork is lined with shops and workshops, wherein all the members of the Artificers' Guild ply their trades and sell their wares. It resounds 24-8 with hammering, sawing and other noisy craftsmanship. There is practically nothing that some clever young man or dwarf cannot knock-up, jury-rig, devise a new way of doing or come up with through tinkering. Yes, some of it will be Heath Robinson, but most of the time it'll work, and work well. Many of the heroes of the Discworld books have had cause to use one or other of the craftsmen - or dwarfs - found on the Street of Cunning Artificers. Glod Glodsson and Lias Bluestone had Buddy's harp repaired here, for example.
It was also here, presumably, where a tinkering dwarf found that by putting a mesh around a flame he had created the safety lamp, which does not ignite minedamp: instead its flame burns blue to alert the operator, inadvertently triggering incipient warfare.
This is also the street Leonard of Quirm was residing in before he was incarcerated (i.e. in Wyrd Sisters). Since this street is in an ethnic area of Morpork, it is probably safe to assume that Leonard of Quirm had fewer patrons than Leonardo da Vinci.