The ruins of Pergamum, Troy, and Assos, along with the Gallipoli battlefields, are the main draws of the region, but leisurely exploration is also rewarded with fresh air, a cool sea, great food, and havens in the wilderness.
The North Aegean and the Sea of Marmara areas are rich in history, spanning many centuries and empires. Civilizations rose and fell at Troy for 5,000 years, and the ruins of Pergamum date from the time of Alexander the Great. The bustling city of Bursa was the first capital of the Ottoman Empire, before Istanbul. The battlefields of Gallipoli bear testament to the more recent past, World War I, while the backstreets of Ayvalık still echo with the footsteps of the Greeks who lived there until early in the 20th century.
The beaches in this region tend to be more pebbly (and the water a touch colder) than they are in other parts of Turkey, but they're also frequently less crowded. You can see the whole of the region in a week or, if you're based in Istanbul, on separate, shorter journeys. Spend at least one evening watching the sun go down over Homer's wine-dark sea, and you'll agree that the North Aegean has a little bit of everything—and a lot you won't find anywhere else.