Today is the Feast of the Dedication of St. John Lateran Cathedral Basilica in Rome. This cathedral was dedicated on November 9, 324 by Pope Sylvester I (314-335 AD). It was a gift from Constantine to the Christians. Because it is the cathedral, it is the seat of the bishop of Rome. And because the bishop of Rome is also the bishop of the Catholic Church, this cathedral is uniquely the parish of all Christians, and hence the tangible locus of communion for all Christians. This basilica is superior in rank even to St. Peter's Basilica in the Vatican. The popes resided here from the fourth century until St. Peter's was constructed in the 16th century. In the baldacchino are the skulls of the Apostles St. Peter and St. Paul. Shawn Tribe has some beautiful photos of this basilica here. Read more about it here.
H/T: Fr. Ray