On The Way To Jerusalem recounts the tale of a nun walking around the cloister for three years to simulate a journey to Jerusalem.
Assuming she walks at 2miles/hour (not very fast) for 8 hours a day (leaving plenty of time to rest) and six days a week (resting completely on Sunday) I make that around 15,000 miles or 24,000km - more than half way around the world.
She should have picked a more sensible route!