Both parts were pretty powerful. Athens was based to its unbeatable navy with the aid of which invaded the territory of their enemies. Sparta, on the other hand, had attacked Attica several times and caused damages the country around the city but not to the city of Athens as this latter was strongly fortified. Since a considerable number of the population of Attica was obliged to take refuge within the city, epidemics soon broke out which killed a lot of people, among whom Pericles who died in 427 b.C. Several city states expressed their will to leave the Athenians or remain neutral in the conflict, but Athens took tough measures against them and some of them were destroyed; Melos, Mytilene and Plataeae are the most striking cases.
In this period lived and worked in Athens Socrates, the famous philosopher, and the comedian Aristophanes, who opposed to the war and many of his works deal with war and peace. Despite the war, the works within the city continued: new temples and other buildings were constructed in these times, as the Aesculapium at the foot of Acropolis, the Erechtheion and the temple of Athena Nike.
Following a short period of peace after 421, the war continued with the venturous expedition of the Athenians in Sicily, which proved catastrophic for the city and its power. The expedition was an idea of Alcebiades, a young aristocrat notorious for his loose life. Alcebiades did not participate to the expedition as he was arrested by the authorities, because he had drunk and caused damages to some of statues of Hermes standing along the roads of the city. In Sicily, the Athenians, having failed to conquer Syracuse, an ally city of Sparta, were defeated by the locals who were strongly assisted by Spartans. The Athenian army was totally destroyed. In 413 b.C., when the bad news arrived in Athens, the people was totally confused and upset. At the same time, Spartans had occupied the fort of Dekeleia, some 20 kilometers northern to Athens, thus constituting another constant danger for the city. In addition, some 20.000 slaves working in the mines of Lavrion escaped to Spartans, thus depriving the Athenians from one of the most important incomes they had.
However, Athens didn’t surrender. Using the funds of an emergency deposit they had established some 20 years before the war, they built a new fleet. But this too did not prove efficient against the Spartans, who had now allied with the Persians. The fleet was destroyed in Asia Minor by the Spartan general Lysandros, at the mouth of Aegos Potamoi, in 405 b.C. In Athens the news of the new collapse signaled the definite end of its power. A few months later, in 404 b.C. it surrendered to the Spartans whose first measure was to demolish the Makra Tehe (the “long walls”) of the city.