From Discworld & Terry Pratchett Wiki
Broad Way is the central thoroughfare of Ankh-Morpork, beginning at the foot of Pseudopolis Yard in the Isle of Gods and running Hubwards-by-Widdershins across the Brass Bridge to the Patrician's Palace, which it surrounds by splitting into Turnwise and Widdershins Broad Way. It then continues to the Hubwards Gate. It is divided into Upper and Lower Broad Way by the Brass Bridge. With typical disregard for spelling conventions, it is often written as Broadway, as in the official mapp. The same Morporkian logic that makes Short Street the city's longest causes the elevated portion on the Isle of Gods to be called Lower Broad Way and the low side Upper Broad Way. In Thief of Time and Thud!, we learn that the Royal Art Museum is also located here. it is also the location for the Royal Bank of Ankh-Morpork.
Another multiversal convention centers the theater district on Lower Broad Way, starting at the Opera House in Pseudopolis Yard and passing The Dysk and the Bear Pit. This resonates with the Roundworld Broadway in New York, upon which are many of the world's finest theatres and all the best plays are performed.