The Madaba Map and Salvation History

Recently while revisited Madaba, Jordan and the famous Madaba Map, I picked up a little book by Herbert Donner on the map. In the book, he writes about the purposes of the map and I found the following statement interesting.

One of the superior purposes, however, is the realization of the exceptional idea, totally unknown before the 6th century, to illustrate God's salvation history in a map. On the mosaic map both Testaments, Old and New, are represented and the holy sites are displayed to the spectators eyes. 

The Mosaic Map of Madaba (Kampen, Netherlands: Kok Pharos, 1992), 30.