While looking at the idea of cities as living things, several things came to mind.
The first was the legend of the vanishing isle.
The vanishing island is supposed to be an island that appears in various spots around the world for a short amount of time and then vanishes again. The legend says that the reason for this is that it’s on the back of a giant turtle and appears when the turtle needs to surface for air.
The fate of the city is governed by the turtle, if people resided in the city when the turtle dove, they would all drown, if fish were swimming in it when it surfaced, they would be choked to death. As well as this, the city is so hard to find that no one really knows much about it as it is continuously moving and changing as the turtle swims and grows and travels
This made me think of Terry Pratchett’s Discworld.
The world where Pratchett’s books take place is flat and carried by four elephants that stand on the back of a giant turtle, swimming through space. When you reach the edge of the world, you’d just fall off entirely.
The people of Discworld rely on this turtle entirely to sustain their world, carry it in the motion around the sun for their calendar, heat and light. The world simply wouldn’t be able to exist without the turtle.
I also thought of the creatures in the game Shadow of the Colossus
These colossi are so big that, like the turtles of the vanishing isle and Discworld, they could probably sustain cities. As well as this, many of them appear to have plants growing all over them.
The final colossus in the game, Malus, has also been given the name the tower because he is so big and looks like his body is one huge building.
Others such as Quadratus and Pelagia, walk on all fours in a way that could give space for a moving city to be built on top.
All of these examples bring in an element of movement, which reflects the ever-changing feel that most cities have. Almost nothing in a city is a constant, people come and go, old buildings get destroyed and new ones get built and the borders of the city are ever expanding.
There is something very fantastical and beautiful about moving cities and using these as a reference, it could be something very interesting to explore.