69tion requires multiple points of view. A convex form screens
something from view, pushes forward, and causes movement
to rebound. At the same time, it curves away from the be-
holder, drawing the > gaze into the distance by guiding it
around the form or > body. The gaze may thus be guided
again towards a concave form, one composed of adjacent ar-
chitectural masses, such as the contours of a public square.
Basically, the relationship between concave spaces and
convex bodies may be of two kinds: hollow spaces exist in-
side bodies or between them. In the first instance, a space is
hollowed out of the body (Latin: concavus), and appears con-
vex from the exterior. In the second instance, a number of
(convex) bodies are combined to form a hollow space. One
and the same convex body, then, may contain concave space
within itself, and at the same time contribute through its exte-
rior to the (concave) formation of a > public square.
As the ‘Janus face’ of the > space-body continuum, this
interplay between concavity and convexity is fundamental
for the shaping of architectural space, as characterized by
Herman Sörgel: ‘Spatiality in architecture consists not of an
interior cavity and an external body, but of inner and exte-
rior hollow space.’ (1921/1998, 243) But as noted by Fritz
Schumacher, the convexity of an architectural body partic-
ipates in this interplay as well. Containment by a concave
form may be interrupted at isolated sections by protruding
convex figures, which invite us to circumambulate them or
to enter their concave interiors. One circulates, for example,
within the concave interior of a square, which itself is formed
by the isolated architectural bodies that stand around it, by
the fronts of buildings that stabilize movement from without.
At the same time, every individual convex architectural body
can be circumambulated, and provides stability as the cen-
tre point of this movement. However, where the architectural
body forms the perimeter of a square, the two operations con-
verge, so that concave and convex effects are superimposed.
Once a building has been entered, and assuming the interior