Giacomo della Porta was the architect of what famous church in Vatican City Italy?

Giacomo della Porta's most famous church is probably the "Chiesa del Gesù" (lit. Church of the Gesu) in Rome. He also participated in St. Peter's Basilica in Vatican (if I'm not mistaken, he worked...

St. Peter's Basilica, see the link below:

St. Peters Bascillica.

St. Peter's Basilica

Rome, Italy. It is considered a separate country.