Giacomo della Porta was an Italian architect and sculptor, who worked on many important buildings in Rome, including St. Peter's Basilica. He was one of about 7 architects for the building of St. Peter's Basilica.
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 on it's impressive dome). He worked on different churches (and fountains) in Rome, but I think the only one in Vatican City is the Basilica (the project for this church is originally by Bramante, but most great architects during renaissance gave their interpretation, until Carlo Maderno completed it).
Antoni Gaudi
There is only one pope in the Vatican and that would be Pope Francis as of 2014. Pope Emeritus Benedict XVI also resides in the Vatican but has no role in governing the Church.
Vatican City is the residence of the head of the Roman Catholic Church, namely the Pope.
Michelangelo, besides being a sculptor and an architect.
The most obvious is Saint Peter's Basilica, the largest church in the world. There is also the Apostolic Palace which includes the famous Sistine Chapel. The Vatican also has a number of museums.
The Vatican is the smallest independent state in the world and its capital is the Vatican City. It is surrounded by the Italian capital city Rome. The head of the Catholic Church (the Pope) resides in its Apolistic Palace.It is the home of the world famous St. Peters Basillica.
Giacomo Puccini
Perhaps America's most famous architect-frank Lloyd wright
There are many famous churches in Italy. The best known would be St. Peter's Basilica but it is not, technically, in Italy but in Vatican City, an independent city-state surrounded by Rome. St. John Lateran is another famous church since it is the official church of the Pope as bishop of Rome.
He was a famous architect in Australia.
Papal Basilica of Saint Peter, or St. Peter's Basilica, is located in Vatican City which is located in Rome. Rome has a lot of famous churches, but this is probably the most famous one.