michael.vatican.va also known as 18.104.22.168 is the primary nameserver for the vatican.va domain. This makes it the networking center of the Vatican City
The name would seem to be a humorous combination of old Unix custom and Catholic piety. It is somewhat a custom (or was at one time) to name major servers after old pagan gods. Many textbooks on Unix use deity hostnames in their examples.
However, while naming the major gateway to the internet after the Egyptian god of death may be acceptable at an institution of unbridled immoraliety such as Reed College, it would be somewhat inappropriate for the Catholic Church. Thus, some sysadmin there chose to name the Vatican's computer after the closest thing the Catholic Church has to a pagan deity, St. Michael the Archangel. The archangels of Catholicism are, after all, relatively close to what a deity would be in another system of belief.
And while there is also a gabriel.vatican.va and a raphael.vatican.va (both of which resolve back to the same ip address), pinging the names of saints that were human, such as James, Mary and Joseph returns a host not found.
ryano and iandunn have both pointed out to me that Netcraft shows that the Vatican does indeed run Unix, specifically Compaq Tru64 running Netscape server. No word yet on whether there will be a papal bull to settle vi vs. emacs