
''Santa Maria degli Angeli e dei Martiri's facade is the ancient ''tepidarium'' of the
Baths of Diocletian
'Santa Maria degli Angeli e dei Martiri' (English: ''St. Mary of the Angels and the Martyrs'') is a
basilica church in Rome, built inside the ''tepidarium'' of the
Baths of Diocletian. The basilica is dedicated to the
Christian martyrs, known and unknown.
[1] It was also a personal monument of
Pope Pius IV, whose tomb is in the
apsidal tribune that culminates the series of spaces.
The ''
thermae'' of Diocletian dominated the
Quirinal Hill with their ruined mass and had successfully resisted
Christianization.
Michelangelo Buonarroti worked from 1563 to 1566 to adapt a section of the remaining structure of the baths to enclose a church. Some later construction directed by
Luigi Vanvitelli in 1749 only superficially distracts from the grand and harmonious Michelangelesque volumes. At Santa Maria degli Angeli Michelangelo archieved an unexampled sequence of shaped architectural spaces. with few precedents or followers. There is no true facade (''illustration''): the simple entrance is set within one of the coved apses of a main space of the ''
thermae''. The plan is developed from a
Greek cross, with a
transept so dominant, with its cubical chapels at each end, that the effect is of a transverse nave.

The transept, with the Roman columns
The vestibule with canted corners and identical side chapels
[2] leads to a second vestibule— repeated on the far side of the transept— dominated by the over lifesize ''Saint
Bruno of Cologne'' by
Jean Antoine Houdon (1766).
[3] The great vaulted transept gives a striking display of the magnificent scale of Roman constructions, 90.8 meters long, and with the floor that Michelangelo raised to bring it up to the Seicento street level, 28 meters high. Raising the floor truncated the red granite Roman columns (''illustration'') that articulate the transept and its flanking spaces. Michelangelo made the transept 27 m. wide, thus providing vast cubical spaces at each end of the transept.
Santa Maria degli Angeli was the official state church during the Kingdom of Italy (
1870-
1946). More recently, national burials have been held in the church. The church hosts the tomb of
Armando Diaz, the general who won
World War I on the Italian front.
William Henry Cardinal Keeler is the
Cardinal Priest of the ''Titulus S. Mariae Angelorum in Thermis''.
The meridian line
At the beginning of the eighteenth century
Pope Clement XI commissioned the astronomer, mathematician, archaeologist, historian and philosopher
Francesco Bianchini to build a meridian line, a sort of
sundial, within the basilica; it was completed in 1702. The object was threefold: the pope wanted to check the accuracy of the
Gregorian reformation of the calendar, to produce a tool to exactly predict
Easter, and, not least, to give Rome a meridian line as important as the one
Giovanni Domenico Cassini had recently built in
Bologna's cathedral, San Petronio.
[4] This church was chosen for several reasons: (1) Like other baths in Rome, the building was already naturally southerly oriented, so as to receive unobstructed exposure to the sun (2) The height of the walls allowed for a long line to more precisely measure the sun's progress through the year (3) The ancient walls had long since stopped settling into the ground, ensuring that carefully calibrated observational instruments set in them would not move out of place and (4) Because it was set in the former baths of
Diocletian, it would symbolically represent a victory of the Christian calendar over the earlier pagan calendar.

Bianchini's gnomon projects the sun's image onto his line just before solar noon
Bianchini's sundial was built along the meridian that crosses Rome, at longitude 12° 50'. At
solar noon, around 12.15 p.m. (1.15 p.m. in summer time), the sun shines through a small hole in the wall to cast its light on this line each day. At the summer
solstice, the sun appears highest, and its ray hits the meridian line at the point closest to the wall. At the winter solstice, the ray crosses the line at the point furthest from the wall. At either
equinox, the sun touches the line exactly halfway between the these two extremes. The longer the meridian line, the more accurately can the observer calculate the length of the year. The meridian line built here is 45 m long, and is composed of
bronze, enclosed in yellow-white
marble.
In addition to the line to mark the sun, Bianchini also added holes in the ceiling to mark the passage of stars. Inside the dark interior,
Polaris,
Arcturus and
Sirius are visible through these holes, even in bright midday. The meridian line was restored in 2002 for the tricentenary of its construction, and it is still operational today.

The raised space of the tribune
Cardinal Protectors of Santa Maria degli Angeli e dei Martiri since 1844
★ Domenico Carafa della Spina di Traetto (22 Jul 1844 - 12 May 1879)
★ Lajos Cardinal Haynald (12 May 1879 - 4 Jul 1891 )
★
Anton Joseph Cardinal Gruscha (1 Jun 1891 - 15 Aug 1911 )
★
Gennaro Cardinal Granito Pignatelli di Belmonte (27 Nov 1911 - 6 Dec 1915)
★ Alfonso Maria Mistrangelo, Sch. P. (6 Dec 1915 - 7 Nov 1930)
★ Jean-Marie Cardinal Villeneuve, O.M.I. (13 Mar 1933 - 17 Jan 1947 )
★
Paul-Émile Cardinal Léger, P.S.S. (12 Jan 1953 - 13 Nov 1991 )
★
William Cardinal Keeler (26 Nov 1994 - )
Notes
1. By a brief dated 27 July 1561, Pius IV ordered the church built, to be dedicated to the ''Beatissimae Virgini et omnium Angelorum et Martyrum'' ("the Most Blessed Virgin and all the Angels and Martyrs"); impetus for this dedication had been generated by the account of a vision experienced in the ruins of the Baths in 1541 by a Sicilian monk, Antonio del Duca, who had been lobbying for decades for papal authorization of a more formal veneration of the Angelic Princes. A story that these Martyrs were Christian slave labourers who had been set to constructing the Baths is modern.
2. One chapel has the tomb of Salvator Rosa, the other of Carlo Maratta.
3. Of Houdon's ''Saint Bruno'' Clement XIV said that he would speak, were it not for the vow of silence of the order he founded.
4. In fact, Alan Cook remarked, "The disposition, the stability and the precision are much better than those of the famous meridian... in Bologna". (Alan Cook, "A Roman Tercentenary" ''Notes and Records of the Royal Society of London'' '56',3 (September 2002), p. 273.)
External links
★
Santa Maria degli Angeli e dei Martiri alle Terme di Diocleziano official website.
References
★ Touring Club Italiano (TCI) ''Roma e Dintorni'' 1965:317f.
★
Ackerman, James S., ''The Architecture of Michelangelo'' 2nd. ed. 1964:136-41.