Oh cool. What you have there is a replica of part of a famous 6th Century AD Byzantine mosaic map called the Madaba Map, specifically the part showing the City of Jerusalem.

The original mosaic was created between 542 and 570 AD in the city of Madaba in modern Jordan, in the Church of Saint George. It's actually one of the earliest cartographic depictions of the Holy Land, and has given us a lot of really important information about the Holy Land in this period. Here's an illustration of the whole map. As one of the oldest geographic floor maps, it played an instrumental role in identifying some archaeological sites in the Holy Land, such as Ashkelon (the piece in the middle with an arrow labeled 7). Its depictions of the larger cities also have proven to be accurate, and very important for archaeology. For example, the Madaba Map depicts the Nea Church in Jerusalem, which was later excavated and shown to be in the same location as illustrated in the map. It's one of the important sources for information about the Holy Land in the 6th century AD.

For further reading on the Madaba Map on the Internet, check out

http://www.christusrex.org/www1/ofm/mad/

this is a site that is an expanded version of a chapter in the book M. Piccirillo - E. Alliata (Eds.), The Madaba Map Centenary 1897-1997. Travelling through the Byzantine Umayyad Period. Proceedings of the International Conference Held in Amman, 7-9 April 1997 (SBF Collectio Maior 40), Jerusalem 1999. It's got lots of images and descriptions and other resources for learning about this particularly important and informative artifact.