For 10 points, name this city whose dispute with Athens was an instigating factor of the Peloponnesian War.
A tyrant of this city was the father-in-law of the Athenian traitor Cylon and rose to power by slaughtering rich men's cattle. This city of Theagenes was home to the 6th-century aristocratic poet Theognis and a 4th-century philosophical school founded by Socrates' pupil Euclid. This city derived its strategic importance from its twin ports, Nisaea and Pegae, which gave this city access to both the Corinthian Gulf and the Aegean Sea. Originally a colony of Corinth, this city established two colonies on the Bosphorus that became Chalcedon and Byzantium. This city's violation of territory sacred to Demeter (*) was the pretext for a punishment levied against it in 432 B.C., forbidding its merchants from trading in the ports of the Delian League. That embargo against this city, along with the quarrels over Corcyra and Potidaea, exacerbated tensions between Athens and Sparta. For 10 points, name this city whose dispute with Athens was an instigating factor of the Peloponnesian War.
A tyrant of this city was the father-in-law of the Athenian traitor Cylon and rose to power by slaughtering rich men's cattle.
Megara