while in rome, he met piotr skarga and stanislaus hosius, who convinced him to convert from calvinism to catholicism, as later did his other brothers, many upon his insistence. he was also known for his cultural and charity sponsorships. he was a founder of many cloisters, hospitals and churches. one of the chapels in the jesuit church in nesvizh, founded by mikołaj krzysztof, would become the family's mausoleum for the radziwiłłs, serving them for the next two hundred and a half centuries. in nieśwież, which became his seat, he also built a fortified castle. he was a patron of artists and scientists; for example he supported the works of cartographers such as tomasz makowski.