The early Greek settlers of Byzantium were led by Byzas, who gave his name to the city. Byzantium was strategically located between the Black Sea and Mediterranean with a natural harbor of the Golden Horn. The Byzantine style of architecture used lime concrete, bricks, marble, mosaics, and domes supported by pendentives. Two important early examples are the 6th century Church of Sergius and Bacchus in Istanbul, with its 15.8 meter diameter dome on pendentives, and Hagia Sophia in Istanbul, known for its massive central dome supported by semi-domes and exedrae.

1. THE EARLY GREEK SETTLERS FROM MEGARA WERE LED BY
BYZAS,FROM WHOM THE NAME BYZANTINE WAS DERIVED.
MEGARA

2.  CITY IS SITUATED BETWEEN BLACK SEA AND
MEDITERRANEAN SEA.
 IT HAS NATURAL HARBOUR OF “GOLDEN HORN” .

3. • Use of lime concrete continued.
• Use of bricks for dome construction
• Marble for ornamental work.
• Flat roofs with small openings in hot weathers and sheltered arcades
surrounded the open courtyards. Oriental dome is the chief feature of the
byzantine.
• Painted figures . statues were absent.

4. DOMES
• Church within a square, with a dome over its centre, usually four
cross- like arms either square ended or apsidal ended.
• Emphasis on its vertical axis
• Non- figural motifs covered all the vault surfaces.
• Large windows flooded the interior with light that
caused the marble and mosaic to glow with radiance

5. • Simple
• Compound
• Melon shaped
• Onion shaped.

6. • Centralized type of plan.
• Independence of component parts.
• Domes made by means of spherical pendentives.
• Constructed by bricks or of light porous stone (pumice)
or pottery.
• Constructed without temporary supports (centering).
• Windows in lower portion.
• Grouping of domes.
• Great height.
• Exterior design pattern in brick work.

7. • Interior covering with marble mosaics and fresco.
• Concrete made from lime sand with crushed tiles and bricks.
• Use of columns for decoration and structurally to support the
galleries and semi- circular arches.
• Mouldings were rare.

8. PENDENTIVES
• It is a curved support shaped
like an inverted triangle.
• It is used to hold a dome.
• Using pendentives, Byzantine
architects could build a higher
and wider dome.
SQUINCH
• It is used to provide a transition
from square to polygon.

10.  S. S. SERGIUS, ISTANBUL(527A.D.)
• Built by Justinian.
• Plan 33m x 28m.
•4 colonnaded exedrae and dome supported on spherical
pendentives 15.8 mt. dia. 22 mt. high

12. However, the building's
present external aspects are
much changed from the
original appearance; the first
dome collapsed in 558 and
was replaced by the present
one, greater in height and
stability. Huge buttresses
were added to the
Justinianic design, and four
Turkish minarets were
constructed after the
Ottoman conquest of 1453,
when Hagia Sophia became
an Islamic mosque.

13. HAGIA SOPHIA ELEVATION
• Built for Justinian by
the architects
authemius &
isodorus.
• Atrium triple portal-outer
narthex double
storey main narthex
(200 feet x 30 feet).
• Centre space 32.6
mts. Square.
• 4 semi circular
arches which rest the
dome 32.6 mt. dia
and 54.8 mts. above
ground.
• 4 massive stone
piers 7.6mt x 18.3
mts.
PLAN

14. • E & w of central space hemi cycles,
covered with semi-domes.Thus
enclosed great oval nave 68.6 mt. x
32.6 mt.
• Hemi-cycles are flanked by exedrae
covered with semi domes that act
as buttresses to the central dome.
• Lead is used as cement to bind the
stones together.
• The forty windows create the
illusion that the dome is resting on
the light that comes through them--
like a "floating dome of heaven."