#1. Bursa
Modern, industrial Bursa is built around the mosques, mausoleums and other sites from its incarnation as first Ottoman capital. Despite being built-up and somewhat chaotic, its durable Ottoman core and abundant parks keep it remarkably placid in places.
For some fresh air after pounding the markets, the soaring peaks of Mt Uludag (Turkey's premier ski resort) are nearby, with Çekirge's thermal hamams en route.
Bursa was awarded Unesco World Heritage status in 2014 for being the birthplace of the Ottoman Empire. The city's historic contributions to Islamic development have given it an austere reputation. Yet locals are kind and welcoming, and you can take the occasional photo inside historic religious structures (just be respectful). You'll see a majority of headscarved women here and devout prayer in overflowing mosques.