As Don Jim Tucker has already 'blogged today's feast of the Dedication of the Lateran Basilica I'll keep it brief. One of the things that the reformers of the liturgical calendar got right after the Council was their policy of ensuring that there was a 'Roman flavour' to the calandar - so the feasts of several Roman martyrs and churches were retained on the General Calendar.
For your 'edification' (if I might pun...) here's an article about the Mother of All Churches and some images. BTW, above the altar are kept the heads of SS. Peter and Paul.