Ayvalik is first of all known for its pretty beaches and the best fish of the country. You will keep long souvenirs of eaten fish at the harbor with sunset in the background. 
Old Ayvalik has more the aspect of a Greek rather than a Turkish village : winding streets with wooden houses which are unfortunately not being renovated.
Around Ayvalik : 
Sarimsakli : 8km from Ayvalik; beach lovers will find a kilometer long white sandy beach.
Seytan Sofrasi (Devil’s Table) is a hill from where one has a marvelous view on Ayvalik and its bay with countless islands.
The Alibey or Cunda island : can be reach by dolmus or in the Summer by boat (recommended). You will come here for a little walk and visit some of the numerous monasteries, enjoy sunset and eventually have dinner.

The antique Kydonia is today a small village opposite the Greek island Lesvos. Ayvalık has been completely destroyed during the Greek Independance War (early XXth century) and lived in 1923, after the Freedom Treaty of Lausanne, the people exchange : half a million Greeks were to leave Asia Minor while Turks left Macedonia, Crete and Lesvos.
Today, the only richness of the village are the remaining of Orthodox churches and monasteries and nice fish restaurants at the harbor.