This 1997 video by English historian John Romer is my all-time favorite historical documentary. It doesn't actually tell you all that much factually about the history of Byzantine Empire, but it succeeds brilliantly in conveying the richness of that culture, which is much kore imporatant than the details of its history anyway. For all its long existence, the Eastern Roman Empire's principal importance was not an an empire or a world power but as a cultural power. The great church of Hagia Sophia in Constantinople (which I avoid calling Istanbul every chance I get) will always be its greatest achievement. By contrast, almost any other empire you can think of is measured more by its power or geographic scope. No one will measure the British Empire by St. Paul's or Westminster Abbey, or the U.S. by the Golden Gate Bridge or the Panama Canal. By contrast, the Byzantine Empire's power and significance was based largely on its cultural significance - its richness and wealth - rather than its geographical extent.
Romer's enthusiasm for the subject is infectious, and to say that the music is haunting is a severe understatement - it is the heart and sould of the program - leave everything out but the music and the images of the churches, and you still have the better half of the series. I first bought this video several years ago and have been waiting for the DVD to come out. It finally did very recently, and I just got it in and watched it in the media room. The image quality is not that great, as you'd expect from a program that was originally shot in video (I presume) but it's close enough, and on a big screen it accurately conveys the buildings and interiors in such a way that you do feel like you're there.