Simplify the following text for a Grade 9 native English-speaking person.
Original: In his early twenties Caravaggio moved to Rome where , during the late 16th and early 17th centuries , many huge new churches and palazzi were being built and paintings were needed to fill them .
Simplified: Huge new churches and palazzi were being built in Rome in the decades of the late 16th and early 17th centuries , and paintings were needed to fill them .