The city of Ankh is one half of the still bigger city of Ankh-Morpork. It is home of the cream of society, or at least these bits that float at the top.
Cities spanning a river are almost always built like this. One bank is higher, drier, cleaner and cooler and that's where the aristocracy and the well-to-do live (together with their moats and duck islands); the other side is a flood plain or disease-infested swamp where the lower classes live. Turnwise of the Ankh there is first the mound of the Isle of Gods and then a rise to the Tump. A lttle distance up the slope, some say, the smell of Morpork is hardly noticeable.1
Most of Ankh-Morpork's business is done in Morpork. The centers of power at the palace and the university, most of the industry and commerce, apart from the Phedre Road area and the docks rimward, are across the river. Ankh comprises mostly mansions, parks, homes of the upper-middle class and the West End/Broadway-like theater district of the Isle of Gods. It can afford such frivolous uses of land as Hide Park, the Tump, Mort Lake and the racetrack.
1 If your olfactory nerve is callused after a morning in Morpork, anyway.
The Online Mappe
There is an extremely good interactive map of Ankh-Morpork on the French-language Discworld site Vade Mecum. It may be accessed in French or English.