Holy Land

The Holy Land was where Vicki Pallister guessed, and the First Doctor tacitly allowed, that they had landed and discovered Richard the Lionheart. It was a generalised regional name for the setting of the Crusades on Earth. Some of the cities in the Holy Land were Jaffa, Jerusalem and Basrah. (TV: The Crusade)

Behind the scenes
The Crusade doesn't define "the Holy Land" in any meaningful way, and the novelisation completely avoids the term.