I ran across this academic paper and thought it might inspire some ideas for the city in the sky.
"Abstract— This paper addresses the self-assembly of a large
team of autonomous boats into floating platforms. We describe
the design of individual boats, the systems concept, the algorithms,
the software architecture and experimental results
with prototypes that are 1:12 scale realizations of modified
ISO shipping containers, with the goal of demonstrating selfassembly
into large maritime structures such as air strips,
bridges, harbors or sea bases. Each container is a robotic
module capable of holonomic motion that can dock in a
brick pattern to form arbitrary shapes. Over 60 modules
were built of varying capability. The docking mechanism is
designed to be robust to large disturbances that can be expected
in the high seas. The docking mechanism also incorporates
adjustable stiffness so that the conglomerate can comply to
waves representative of sea state three, and have the ability to
dynamically stiffen as required. The component modules for
autonomous assembly, docking and simultaneous collision-free
planning as well as the software architecture are presented
along with the description of experimental verification."
Full article:
http://www.seas.upenn.edu/~juse/dtemp_full.pdf