The exterior of the church, from the broad sweep of steps on Via Cavour to the more elaborate facade on Piazza Santa Maria Maggiore, is that of a gracefully curving 18th-century building, a fine example of the Baroque architecture of the period.

But in fact Santa Maria Maggiore is one of the oldest churches in Rome, built around 440 by Pope Sixtus III. One of the four great pilgrimage churches of Rome, it's by far the most complete example of an early Christian basilica in the city -- one of the immense, hall-like structures derived from ancient Roman civic buildings and divided into thirds by two great rows of columns marching up the nave.

The other six major basilicas in Rome -- San Giovanni in Laterano and St. Peter's Basilica are the most famous -- have been entirely transformed, or even rebuilt. Paradoxically, the major reason why this church is such a striking example of early Christian design is that the same man who built the incongruous exteriors about 1740 -- Ferdinando Fuga -- also conscientiously restored the interior, throwing out later additions and, crucially, replacing a number of the great columns.