Basilica di San Giovanni in Laterno
(St. John Lateran)
"The Cathedral of Rome and of the World"
Dedicated to both St. John the Baptist and St. John the Evangelist, the Basilica of St. John Lateran is the first among the four major basilicas of Rome, but receives its august title because it is also the cathedral of the bishop of Rome, the Pope.
Built by Constantine the Great in the 4th century, San Giovanni in Laterano was the first Christian church built in Rome. It was embellished with beautiful decorations given by Constantine, including seven silver altars with seven gilded candlesticks inlaid with images of prophets; 111 chandeliers; and gold voil for the apse vault.
There were seven oratories surrounding the basilica dating back to the fifth century that were eventually incorporated into the church. The devotion of visiting the oratories of this basilica, led to the devotion of the seven altars, still common in many churches of Rome and elsewhere.
For more history and tons of pictures go here. For the very complete history, go to the Catholic Encyclopedia, here.
For a little more information, you can go back a couple days to the post from Holy Thursday, which was also stationed at St. John Lateran.