I'm reading a history of Sparta right now, and the author is discussing arhaic Tegea and Arcadia as if the latter were comprised of many cities, and makes similar claims about Messenia. He also talks about attempts by Elis to conquer Olympia. All of this makes me wonder...
We always think about Greek city states as being like Athens - with a single dominant city. A city state with multiple major cities is sort of a contradiction in terms. How common were multi-polar states, with multiple significant cities? How did they work compared to the more classical states like, say, individual Aegean islands or Athens?
If they weren't common, am I interpreting the author wrong?
Side question: Does anyone know a good book covering the broad sweep of ancient Athenian history?
When we think about Ancient Greece, we tend to think of a swathe of the Eastern Mediterranean marked "here be city-states". And indeed the Ancient Greeks generally spoke of themselves as citizens of a polis - a confusing multi-purpose word indicating both a political community and its main urban/defensive hub. But this is a simplification. There were many kinds of overlapping political organisations in the Greek world, and the edges of the concept of "city-state" are blurry.
Some communities, especially on small islands, would form a state with one urbanised centre and a unified hinterland. These are perhaps the easiest to define as city-states (though most of them would be very small; the average polis had fewer than 1000 citizens).
Other communities were formed over time as smaller villages and groups banded together into a single political community without losing all of their local/regional identity. Sparta is a great example; the urban centre known as Sparta was composed of five villages and even in the 4th century BC some of these retained religious festivals that were not shared by the others. In the 380s BC, Sparta cynically argued that the villages that had merged centuries ago into the polis of Mantineia deserved to be independent, and destroyed the power of this Arkadian neighbour by splitting it back up into its constituent villages.
Other communities emerged when smaller states, sometimes poleis in their own right, decided to physically merge and build a new shared urban centre, in a process known as synoikismos ("living together"). Athens believed it was formed in this way, although the settlement at the Akropolis dates to the Bronze Age and its territory also retained a number of significant secondary urban centres like Eleusis and Acharnai. More historical examples include Olynthos, which became powerful when it absorbed several neighbouring populations in 432 BC, and Rhodes, a new city and community formed out of the union of all 4 city-states on the island around 408 BC.
There were also states that consisted of several smaller poleis dominated by a larger one. In theory the smaller ones might try to be independent, but this was often impossible given the sheer imbalance in resources; for example, the mid-sized polis of Elis had no trouble controlling tiny nearby Olympia unless Sparta intervened. Sparta itself was of course an example of the same power structure, holding Messenia and other regions in subjection. But the most contentious example in the Classical period was Boiotia, a federation of theoretically equal poleis dominated by Thebes. Over the centuries, Thebes was sometimes able to control some, sometimes all of the poleis of the region, but major wars were fought to keep Boiotian towns like Plataiai, Haliartos, Orchomenos and Thespiai independent.
Other communities banded together in so-called federations while retaining their local autonomy. It's not always easy to distinguish between this category and the last one; Boiotia liked to call itself a federation even though Thebes was clearly its largest and most powerful member. Thessaly was technically a federation, but one dominated at times by one or the other of its major poleis (Pherai, Larissa, Pharsalos). But other federations were more egalitarian, and their federal councils could muster significant military power: the Arkadian cities, the Chalkidian League, Phokis, Lesbos, and so on.
Finally, there were the so-called "ethnos states" - regional political communities with few real cities, often in the more remote parts of Greece, who were united in culture and for their defence but otherwise didn't really look like poleis to Greeks from more settled areas. The Aitolians and Akarnanians of Western Greece, the Achaians of the northern Peloponnese, the inhabitants of the wilder parts of Central Greece, Thessaly, and Crete, and even upland Arkadians are often characterised as ethnoi rather than city-state Greeks. Recent archaeology has often pushed back the boundaries of ethnos Greece, asserting that there really were poleis worthy of the name in regions like Phokis and Lokris, but there was certainly a perception even among the Ancient Greeks themselves that some parts of Old Greece simply weren't urbanised and divided up into poleis.
When we read histories of Athens and Sparta and their respective empires, we're mostly learning about long-unified political communities subjecting others and increasing their power. But as they did so, they came into contact with the full range of different states known to the Greeks, many of which came into existence precisely to defend against encroachment by larger powers. Most of the wars of Greek history happened because of disputes over which larger centre could control which smaller ones, or because existing powers grew concerned about the military potential of newly formed federations, synoikismoi and alliances.