Where the Apostles went

St. Peter (mainly) preached in Rome where he served as its first bishop, was then crucified head downward on the Vatican Hill and his bones rest beneath the high altar of his basilica there; this was confirmed by archaeologists in 1939 when they found the original tomb with writing “Peter is within.” His feast day is June 30; additionally his (Papal) Seat is celebrated on February 22. 

St. Paul mainly preached in Turkey and Greece, was beheaded in Rome and is buried beneath the high altar of his basilica there on the Via Ostia; in 2009 this was confirmed by archeological research. His feast day is June 30 together with St. Peter; additionally Paul's conversion is celebrated on January 25. 

St. John the Evangelist lived in Ephesus (Turkey, with Mary), was imprisoned on Patmos (Greece) where he wrote the book Revelation, and died back in Ephesus where he was buried as well, all according to ancient tradition. In the 1920s archaeological teams found St. John’s tomb, but it was empty and no-one knows what became of his body. His feast day is December 27.

St. Andrew, the brother of St. Peter, preached a.o. in Russia and the Ukraine, served as the first bishop of Constantinople, was martyred on what is since called "Andrew's cross" and buried in Patras (Greece); later his relics were taken to Amalfi (Italy), but in 1964 some of them were returned to the apostle’s original tomb. His feast day is November 30.

St. James the Greater, the brother of St. John, preached in Spain, was martyred in Jerusalem (the first apostle); it is said that then his body was miraculously transported to Santiago de Compostela (Spain) and buried there. Indeed beneath the cathedral archaeologists have found a first-century Christian cemetery. His feast day is July 25.

St. James the Less served as the first bishop of Jerusalem, was allegedly thrown from the roof of the Temple, then beaten and stoned to death, and buried on the Mount of Olives. His relics were first moved to Constantinople and later a portion or perhaps all of them to the Church of the Twelve Apostles in Rome. His feast day is May 3.

St. Philip, it is said, was nailed by his feet to a tree, upside down, and ultimately beheaded in Hieropolis (Turkey); his relics rest with those of St. James the Less in the Church of the Twelve Apostles. In 2011, archaeologists found the original tomb of Philip in Hieropolis, but it contained no human bones. His feast day is (also) May 3.

The immensely popular St. Jude Thaddaeus and the less-well-venerated St. Simon seemingly preached together in Persia (a.o.), and were both martyred there: it is said that Jude was beaten to death with a club, and Simon was sawn in half; both rest in St. Peter's basilica; their feast day is October 28.

St. Thomas preached in India and it is said that there he was run through with a spear by a Hindu priest. A portion of his bones are venerated in Chennai (India), but most are enshrined in a golden casket within a white marble altar in Ortona (Italy); his feast day is July 3.

St. Bartholomew (also known as Nathaniel) preached in Armenia and was flayed alive there; most of his relics are venerated in Benevento (Italy), but a portion is enshrined on the Tiberina Island (Rome). His feast day is August 24.

St. Matthew, the first Evangelist preached in Ethiopia (south of the Caspian sea!) and seemingly was martyred there as he said Mass; his relics are venerated in Salerno (Italy) and his feast day is September 21. 

St. Matthias replaced Judas as an apostle, was buried in Jerusalem, but his relics were sent to Trier (Germany); his feast day is May 14.

St. Barnabas, not one of the Twelve, yet generally considered an apostle like Paul whom he accompanied for some time; he was a Jew from Cyprus, where he also died and was buried; his feast day is June 11. 

St. (John) Mark the Evangelist was a cousin of Barnabas and his compagnion for some time (in Cyprus), just as of the apostles Peter and Paul; he served as the first bishop of Alexandria (Egypt), one of the five primary Sees of old; his grave is venerated in Venice (Italy) and his feast day is April 25.

St. Luke the Evangelist was a Greek physician from Antioch, and another prominent compagnion of the apostle Paul; the origin of the Marian icons is ascribed to him. He died in Thebes (Greece) and his grave is venerated in Padua (Italy); his feast day is October 18.

St. Mary Magdalene, the "apostle to the apostles", sailed with her siblings st. Lazarus and st. Martha to St-Marie-de-la-Mere (France), did penance in a grotto near St-Maximin-La Sainte-Baum (close to Marseille) where she died, was buried and at least her skull is venerated; it seems her relics were (temporarily) moved to Vezelay where she is also venerated; her left hand is venerated on mount Athos (Greece) and her feast day (since 2016) is July 22.

N.B. St. Mary (Jesus' Mother), as mentioned, lived with the apostle John in Ephesus but died in Jerusalem around the Apostle's Council; of old her grave is venerated next to the Mount of Olives, but never have any real relics been claimed of her (except for some dubious claims for her hair, garment, and sash) in contrast to every other important saint. This is good support for the dogma of her bodily Assumption into Heaven which is celebrated on August 15. Her other important feasts are January 1 (Mother of God), March 25 (Annunciation), August 22 (her Queenship), September 8 (her birth) and December 8 (Immaculate Conception).