Wikipedia doesn't specify the Avar faction's capital. The Avars were a people from modern day East-Central Europe, back in around Charlemagne's time.
However, in a "Total War" game, the Avars' capital was in Szeged, in modern-day Hungary.
Was there any real evidence to suggest that they had their capital in Szeged? (If not, where'd the game get the idea that brought them to that decision?)
By the way, whatever happened to the Avars later on? How'd they cease to be around?
I am assuming the TW game that mentions them is Attila since that would fit the time frame better than Rome II would. Naturally Creative Assembly sort of has to give each faction a capital in game, although the nature of 'capitals' in the early middle ages is a different discussion. On to your question though, whether there was in fact an Avar capital.
As far as before the 8th century my knowledge of the Avars is extremely limited, so I won't address that here. Instead, from the 8th century onwards they appear in sources relating to the Carolingian empire, and its there that we might get some clues to their capital. In the Annales Regni Francorum for 796 we get this information (I'm translating from the original Latin of the revised annalist, since the English translation does not retain the useful bits): 'Pippin^1 with Huns^2 fighting across the river Tisza, and the same palace, that is [the one] called 'the ring'...was destroyed from every part.' Now, what was 'the ring'? There is only one surviving description of what it was, or rather, they were since there were several 'rings'. Notker tells us that the rings were a serious of fortified structures all built relatively close to each other: 'twenty Teutonic miles, that is, forty Italian miles', and that it was here that 'they gathered for two hundred years and even more all the wealth of the entire West'.^3 Taken together this sounds like pretty good evidence for some type of 'capital', so where did CA get Szeged from?
The key is the quote above giving using the information about the battle taking place on the river Tisza, which is the river which runs through Szeged, so it is probable that they got it that way, perhaps from earlier sources that I am not versed in. The sources above don't mention that since by the 8th century it was known as the Ring. If someone with a knowledge of settlement in the earlier period can come along and fill the rest out that would be good.
For your final question, 'what happened to the Avars', the passages above pretty much detail the end of the Avars. After they are conquered in 796 they are hardly ever mentioned again, aside from a brief attempted uprising a few years later.
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