A Tour of the Continent provides some brief descriptions about each city:
Kingsport, capital of the Unified Territories, is a hub of learning and culture. As a port city, it has easy access to the interior of the north, as well as good sea connections to the rest of the eastern coast, even though water-walkers rarely visit it. The city is also home to the Royal Academy of Mages, and the biannual conclave.
Iceholm is the largest settlement of polar bears in the world. Most of the city is carved out of ice, leading to some truly beautiful architecture (about which the author rhapsodizes at some length). Its primary exports are fish and philosophy, and its primary imports are refined metals. The city is governed by a strange kind of foreign government — a "democracy", which gives each of the polar bears who has completed their education a say in the laws.
Remsfield is sometimes metaphorically called 'the turtle of the north'. Despite being stationary, it forms the center of a number of trade routes, and has the largest stationary market in the world. Exports include pretty much everything, although notably a lot of grain.
Treeholm is less urban and more dispersed than the other cities featured in the book, although its total population is actually comparable to Kingsport. Because of its position on the border between the north and south, it has a long history of distinguished battles. It is also the only non-human-majority city within the Unified Territories at time of writing, with pixies and fairies making up more than half of the population. Exports include living plant-based materials and artisanal goods.
Merriterra is fairly isolationist, and difficult for outsiders to access. Consequently, little about it is known. They maintain a trading post on the surface, where they mostly interact with water-walkers and the few human ships brave enough to leave the coast.
Crossing Ways is the largest mobile city, being more like a constantly changing network of barges, ships, and carts built on the surface of the ocean. When it ranges north, it can sometimes be seen from the coast with a telescope. It is technically accessible to humans, but most find the city hard to navigate.
Dragon Mountain is the center of dragon culture and learning. Carved from a single mountain, it is rumored that the tunnels extend deep underground. The mountain is also known to anchor potent protective spells. The fact that it is sized for dragons means that the buildings and corridors are uncomfortably large for humans to navigate, which in turn inspired the creation of a kind of cart that is hauled on a track up and down the mountain to provide access to the different levels.
On the turtles, it has this to say:
Theresa, oldest of the turtles, can usually be found near the southern edge of the grassland. She specializes in textile manufacturing, and has a fondness for tea.
Taylor is a mid-sized turtle. They enjoy swimming, and therefore tend to hang around on the eastern coast.
Terrance is the most far-ranging of the turtles, being found nearly anywhere within the grasslands. He specializes in glassworks, and collects romance novels. He features the largest library of any turtle.
Timothy is Terrance's younger brother. He patrols the southern border with the desert, and has a reputation as a formidable enemy of pirates.
Terra is the youngest turtle large enough to be called a city. She tends to haunt the border with the forest, and is unique for her high population of fairies. She has the most extensive gardens and living buildings of all turtles.
Thomas is also far-ranging, being found all over the west. He specializes in the spice trade, and boasts the largest merchant bank of any turtle.
Terpsichore is small for her age. She has the most restrictive immigration policies of any turtle, and focuses primarily on the production of art. She is famed for her great concerts, and follows a predictable tour schedule so that fans of the theater may know where to find her.
