The catholic church and the vatican

The Catholic Church, also known as the Roman Catholic Church, is the world's largest Christian Church, with more than one billion members worldwide. It is among the oldest institutions in the world and has played a prominent role in the history of Western civilization. The Catholic hierarchy is led by the Pope and includes cardinals, patriarchs and diocesan bishops.

The Church teaches that it is the one true Church divinely founded by Jesus Christ, that its bishops are the successors of Christ's apostles and that the Pope is the sole successor of Saint Peter who was the first pope named by Jesus Christ.
After its foundation, the Catholic Church faced about 300 years of persecution from the Rome Empire, what made them start to meet behind closed doors.

In 306 (A.D) Constantine became emperor of Rome. His mother Helena became a Christian and urged Constantine to ease up on the persecution of Christians. He decided that Christianity would now be the state religion.

Christianity became more associated with the Empire, resulting in persecution for Christians living outside of the empire, as their rulers feared Christians would revolt in favor of the Emperor.
After the fall of the Western Roman Empire in 476, the Catholic faith competed with Aryanism for the conversion of the barbarian tribes

Due to a land jurisdiction, during the 11th century the church was divided between catholic and Orthodox Church (Eastern Christianity)
Pope Urban II launched the First Crusade in 1095. The Crusades were a series of religious expeditionary wars with the stated goal of restoring Christian access to the holy places in and near Jerusalem. In 2001, Pope John Paul II apologized to the Orthodox Christians for the sins of Catholics including the sacking of Constantinople in 1204.
The sack of Constantinople during the Fourth Crusade left Eastern Christians embittered, despite the fact that Pope Innocent III had expressly forbidden any such attack. (The crusaders inflicted