The Eastern Romans had well-developed towns and cities in Anatolia, while the Turks were mainly nomadic and pastoral, so that after the Turks took over Anatolia, the towns and cities in the interior declined severely, and central Anatolia become kind of an Asian wasteland. At least that's how I read it.
(Note that I've sworn off the term "Byzantine"!)
I’ve never been fond of it, never made a lot of sense, actually, but since they were good at business, the “byz’ part is easy to remember. ;’)
Their last really kick-ass ruler was Boris the Bulgar-slayer; this page about him damn near mede me wet my pants when I read it.
http://www.badassoftheweek.com/basil.html