Coming from the bland residential architecture and coal smoke of Istanbul, the Prince's islands are literally and figuratively a breath of fresh air. Just dots in the Sea of Marmara, these islands boast some stunning Victorian summer villas built by wealthy Ottomans over the years and a few rich Istanbul residents that live here year round.
On the island of Buyukada, no cars are allowed, so you can also avoid the country's notoriously bad drivers. (In my three trips around the globe, the Turks get the prize for recklessness and just plain inability to drive).
After arriving on the ferry from Istanbul, you can rent a bike right at the dock and then make your way around the island at your own pace. There are some steep hills, but the vistas are fantastic. There are plenty of big trees providing shade and you'll want to stop and gape and some of the amazing architecture, especially if you've been seeing nothing but mosques and boring apartment blocks.
When you get tired, you can grab some good Turkish food, an Efes beer, and the wafting smell of the sea.