The first Apostle called by Jesus was Andrew, who had previously been following John the Baptizer. Upon encountering Jesus he became his follower along with his brother Peter. Eventually both left their livelihood of fishing to become "fishers of men".
There is not a lot of recorded history regarding Andrew, but it is believed that after the Ascension of Our Lord he traveled to Greece to preach the Gospel.
During the persecution of Christians by the Emperor Nero he was arrested and later crucified on an X-shaped cross. He was tied, not nailed, to the cross and suffered for two days before dying all the while preaching to those around him.His relics were first taken to Byzantium and then on to Scotland sometime in the Fourth Century and later returned to Greece. He is the the patron saint of many countries such as Barbados, Ukraine, Russia, Romania, Patras in Greece, Amalfi in Italy, Luqa in Malta, and Esgueira in Portugal. In addition, he is the Patron Saint of the U.S. Army Rangers.
But he is honored most, perhaps, in Scotland. The national flag of Scotland bears the X-shaped cross and his feast day, November 30th, is a national holiday.
The relics are kept in Patras in the Church of Saint Andrew.
The city is most normally visited by ferry or bus from Athens.
The Basilica is not Roman Catholic, it is Greek Orthodox.