In the Pax Era, Castel Gandolfo is a herded and terraformed asteroid in Pacem System, one of many other orbital habitats around Pacem such as the Torus Mercantilus and Castel Sant'Angelo.  It was the Pope's "summer retreat". The potato-shaped little world was more than forty klicks long and twenty-five across. Its sky was blue, with its oxygen-rich atmosphere held in by containment fields. It had hillsides and terraces green with grass and crops, the sculpted mountains forested running with streams and small animals. It looked like an ancient Italian village from the outside, while the interior of asteroid was honeycombed with garrisons holding more than ten thousand Swiss Guard and elite Pax troopers.