University of Virginia Library

AACHEN, PALACE CHAPEL. TRIBUNE

DETAIL, BRONZE RAILING, CA. 800

Eight such railings, each 4 feet high and nearly 14 feet long, were each cast in one piece:
an astonishing accomplishment of the Carolingian Renaissance. Roman grille work patterns,
Byzantine acanthus leaves, and Hiberno-Saxon scroll-and-grid motifs are subsumed in
a sophisticated medieval linearism.

71.X AACHEN: THE CITY CENTER. A CADASTRAL PLAN AFTER 1800 WITH
CHARLEMAGNE'S PALACE GROUNDS

Superimposed in red are the grounds and buildings of Charlemagne's Palace as well as the reconstructed street
system of the Roman town of Aquae Granis (redrawn in part by Ernest Born, after Hugot, 1965, fig. 1 facing
p. 534, and with the aid of Hugot's original drawing which he generously made available to us for that
purpose).

Like most Roman towns or military camps this settlement was internally divided into four quarters by two
main arterials intersecting each other at right angles. The course of these, as Leo Hugot has shown, are
recognizable in the street alignment of the modern city of Aachen. They are: from north to south, the
alignment Kockerell Strasse—Klostergasse and Kleine Marschier Strasse (A-B); from west to east, the
alignment Jakob Strasse and Grosse Koln-Strasse (C-D). The latter was part of a Roman road that led from
Herleen to Kornelismünster into the Eifel Mountains; the former of a road that connected Liège with Julich
and Cologne.

The city of Aachen (French: Aix-la-Chapelle; Italian: Aquisgrana) owes its name to a Celtic settlement and
sanctuary that had sprung up in the vicinity of a cluster of sulphur hot springs which the Romans after their
conquest of this territory, in the first century A.D. converted into a watering place for legionaries, pensioners,
and other civilians visiting or settling there for recreational purposes or for reasons of health. The Romans
referred to this location as Aquae Granis = "the Waters of Granus" (a Celtic deity worshipped in connection
with hot springs). In ancient times, as well as in the Middle Ages and up to our own days, this kind of spring
was believed to have a curative effect on such afflictions as gout, arthritis and scrofula.

At the collapse of the Roman empire the city of Aquae Granis was destroyed (presumably around 375) but the
life of the native population appears to have continued. King Pepin bathed in the springs of Aachen in 765
and ordered the baths to be cleaned. Charlemagne signed deeds in AQUIS PALATIO PUBLICO in 768 and 769,
and between 777 and 786 rebuilt and enlarged his father's palace. The site became his favourite winter
residence from 794 onwards, a date which marks the turning point from ambulant government to rule from a
central seat of government, at least during the winter months, the summers continuing to be taken up by
warfare. Charlemagne furnished the site with a royal Audience Hall and a monumental Palace Chapel (fig.
71.Z), a residence for himself (location and details of construction unknown) as well as a considerable number
of lesser buildings to house his court as well as his bodyguards.

The Palace, as was to be expected, gave rise to the growth of a vast cluster of subsidiary establishments,
mainly to the north and to the west of the royal court, and acquired the appearance of the town when all of
these VICI, together with the Palace, were surrounded in 1172-1176 with a wall by order of Emperor Frederic
Barbarossa.

71.Y SITE PLAN OF THE EMPEROR'S AUDIENCE HALL AND THE PALACE CHAPEL AT AACHEN,
BUILT BETWEEN 796 and 804

KEY TO NUMBERS OF PLAN

1. THE PALACE CHAPEL

2. ATRIUM

3. NORTHERN ANNEX

Metatorium where the emperor changed his attire before entering the chapel

4. SOUTHERN ANNEX

Secretarium for assembly of the clergy and the holding of synods in contemporary sources referred to as In Laterano

5. THE EMPEROR'S AUDIENCE HALL

6. ENTRANCE HALL at ground level connects the OUTER COURT with the INNER COURT

7. BARRACKS for the emperor's guard

Superimposed on Hugot's drawing of a part of the Emperor's Palace at Aachen is shown the rectangular schematism on which its plan is
based. The basic module, as Hugot's dimensional survey of the site has demonstrated, measures 12 feet. Seven basic modules comprise one
major unit. The length of the plan is 7 major units, plus 2 basic modules for the east-west street, plus 1 basic unit for the projection of the
north apse of the Emperor's Audience Hall. Thus the length of the rectangle is 7 × 7 plus 3 units, or 52 units; its width is 4 × 7 units plus
2 units, or 30 units—a rectangle 624 feet long by 360 feet wide.

What captures our attention is the prevailing scheme of numerical and space relationships. The sacred numbers 3, 4, and 7, with 10, 12,
and 40, represent values of measurement that govern or control lines and critical grid relationships and are suffused into the fabric of the
plan to form interrelated kinships. For example, the length of the plan, 52 units, saturated with 75 [(7 × 7) + 3] is the sum of 40 plus 12.
The width of the plan, 30 units, is the product of 3 × 10 and, with 12 as a multiplier, creates 360 feet [(3 + 3 + 3) × 40]. Such a collection
of NUMERI SACRI offers striking evidence of the presence of sacred numbers as a dominating influence in the mind of the Carolingian
planner at the heart of the Empire, at this period in the development of western civilization. The aesthetic consequences of this pervasive
geometric and numerical schematism is another and different problem. Too, it is not without interest that the 3-4-5 triangular relationship
for the formation of a right angle is consonant with the 12-foot grid and would facilitate, in the field, layout for building foundations. In
monumental building schemes in particular, and all building in general, this would be advantageous to both the architect and his director
and construction foreman on the site.

Thus, rectangular schematism, identifiable with esoteric sacred numbers, was well-tailored in some respects to the practical needs of a
builder whose responsibilities, far removed from finely woven webs of theology, were characterized by mundane objectives, intolerant of
hocus-pocus.

E. B.

71.Za AACHEN, PALACE CHAPEL, BUILT BETWEEN 796 and 804

PLAN AND ELEVATIONS BY LEO HUGOT
GRID SUPERIMPOSED BY AUTHORS

The interesting and developmentally crucial significance of Leo Hugot's discovery of modular principles governing the organization of the Palace
Chapel at Aachen is its demonstration, by implication, that even a centrally planned Carolingian building cannot escape the power of
transformation which, at the age of Charlemagne, converts the Early Christian basilica into a modular structure.

The design of the Palace Chapel at Aachen is based on that of the church of San Vitale at Ravenna, begun around 532 and finished in 546.
In both buildings the shape and composition of the primary spaces as well as the formation of the basic morphological features are essentially the
same. In each case a tall octagonal center space with fenestrated and dome-surmounted drum is encircled by a peripheral envelope of outer
spaces, which, although internally divided into two stories (ambulatory and gallery) are, in their combined height, lower than the center space.
In each case the drum with its dome rests on eight huge arches, rising from piers erected in the eight angles of the octagon (cf. fig. 162.B).

These are the basic compositional and structural features. Yet in style and spatial concept the two buildings differ distinctly. In San Vitale the
shell separating the octagon from its spatial perimeter is made up of semicircular niches that billow out into the body of ambulatory and gallery.
Despite their intensive perforation (three arched openings on each level) these curved niches, together with the piers to which they are attached,
are aesthetically perceived as a continuous sheet of masonry stretched around the center space. The movement is encircling, not divisive, and the
enveloped space, being uninvaded by any of the enveloping features, retains its full corporeal solidity and homogeneity. It is sculpture springing
from a concept of spatial mass akin in spirit to the monolithic self-containment of the component spaces of the Early Christian basilica (Cf.
figs. 174 and 177.A-C).

The stylistic and conceptual archetype and prototype of this manner of molding space is the Roman Pantheon, a body of incomparable globular
perfection and beauty contained in a masonry shell of simple cylindrical shape whose surfaces pass in unbroken planar continuity into those of
the semicircular dome by which it is surmounted, with no intrusion at any point. The camera—one-eyed and stationary—is incapable of
capturing this quality of style, but Giovanni Piranesi, with his uncanny sensitivity for such matters, has portrayed it with great perspicuity in a
series of masterful engravings.

The design of the Palace Chapel at Aachen by contrast is based upon the concept of spatial divisibility. This quality is strikingly reflected in the
manner in which the eight component surfaces of the octagon meet and connect with one another. Instead of billowing niches swinging inward and
outward, yet never losing their encircling hold, the Chapel's straight surfaces, separated by sharp lines, rise in undisrupted ascent from the
ground to the apex of the vault by which it is covered. The dome over the octagon of San Vitale is circular (or nearly so) and therefore
detaches itself distinctly from the octagonal shape of the body of space lying beneath it, the transition from octagonal drum to circle of the dome
being achieved by means of squinches. It rests or hovers like a protective lid over the space it covers. The dome over the octagon of the Palace
Chapel, by contrast—a cloister vault, not a hemicycle!—is segmented into eight separate parts, like the eight sides of the octagonal shell that
supports it. The emphasis thus is shifted from connecting surfaces to separating lines. In Aachen, for this reason, the center space conveys the
feeling of being "sliced" or "sliceable" rather than "whole" and "rounded." It could aesthetically be defined as an aggregate of triangular
prisms, meeting with their sharp inner edges in the center axis of the building. This is divisive Carolingian modularity: the conceptual equivalent
of the modular square division of the Carolingian basilica (figs. 166-173); medieval divisionalism versus Classical corporeality.

The differences are discernible with even more striking sharpness in the structural articulation of the outer spaces. In San Vitale, ambulatory
and gallery were covered by timber roofs formed by continuous sequences of beams or trusses all lying on the same level, and therefore visually
perceived as flat and continuous annular planes (the present vaults are medieval; see Krautheimer, 1965, 170). In the Palace Chapel at Aachen
the same spaces are covered, on ground floor level by groin vaults of alternating square and triangular shape; and on gallery level, by rampant
barrel vaults alternating with sharply defined triangular spaces. This is cellular medieval organization of space, springing from the same
conceptual sources that in the longitudinal layout of the basilica lead to the arch-framed bay division of the Romanesque and the Gothic
(fig. 177); and for more visual demonstration, Horn and Born, Viator, 1975, figs. 38, 39.A-B.

Centrally planned buildings do not lend themselves with the same ease to modular division and, for that reason, are not part of the mainstream
of medieval development. One hundred and fifty years after the construction of the Palace Chapel, a sophisticated Florentine architect created in the
Baptistery of that city, a synthesis between classical and medieval, disclosing that even south of the Alps materials inherited from antiquity are
reshaped in a similar manner (cf. Horn, 1938, 99-155; reprinted 1973).

71.Zc FRONT ELEVATION

71.Zb SIDE ELEVATION