Dodecanese relative quiet and prosperity. In 408 BC, the three cities of Rhodes had united to form one state, which built a new capital on the northern end of the island, also named "Rhodes"; this united Rhodes was to dominate the region for the coming millennia. Other islands in the Dodecanese also developed into significant economic and cultural centers; most notably, Kos served as the site of the school of medicine founded by Hippocrates. However, the Peloponnesian War had so weakened the entire Greek civilization's military strength that it lay open to invasion. In 357 BC, the islands were conquered by
Symi the peculiarly colorful neoclassical mansions covering the slopes near the main city date from that period. Although Symiots took part in the Greek War of Independence of 1821–1829, it was left out of the new Greek state when its borders were drawn up and so remained under Ottoman rule. The island, along with the rest of the Dodecanese, changed hands several times in the 20th century: in 1912 the Dodecanese declared independence from the Ottomans as the Federation of the Dodecanese Islands, though they were almost immediately occupied by Italy. The island was formally ceded to Italy in 1923, and