Editing Ancient Roman architecture (section)

== Architectural features ==

=== Mosaics ===
{{main|Roman mosaic}}
[[File:Centaur mosaic - Google Art Project retouched.jpeg|thumb|The Centaur mosaic (2nd century), found at [[Hadrian's Villa]] in [[Tivoli, Italy|Tivoli]], Italy. [[Altes Museum]], Berlin]] 
On his return from campaigns in Greece, the general [[Sulla]] brought back what is probably the best-known element of the early [[Roman Empire|imperial period]]: the [[mosaic]], a decoration made of colourful chips of stone inserted into cement. This tiling method took the empire by storm in the late first century and the second century and in the Roman home joined the well-known [[mural]] in decorating floors, walls, and [[grotto]]es with [[geometric]] and [[pictorial]] designs.

There were two main techniques in Greco-Roman mosaic. ''[[Opus vermiculatum]]'' used tiny ''[[tesserae]]'', typically cubes of 4 millimeters or less, and was produced in workshops in relatively small panels, which were transported to the site glued to some temporary support. The tiny ''tesserae'' allowed very fine detail and an approach to the illusionism of painting. Often small panels called ''emblemata'' were inserted into walls or as the highlights of larger floor-mosaics in coarser work. The normal technique, however, was ''[[opus tessellatum]]'', using larger tesserae, which were laid on site.{{sfn|Smith|1983|pp=116–119}} There was a distinct native Italian style using black on a white background, which was no doubt cheaper than fully coloured work.{{sfn|Smith|1983|pp=121–123}}

A specific genre of Roman mosaic obtained the name ''asaroton'' (Greek "unswept floor"). It represented an optical illusion of the leftovers from a feast on the floor of rich houses.{{sfn|Miller|1972}}

=== Hypocaust ===
[[File:2005-09-17 10-01 Provence 646 St Rémy-de-Provence - Glanum.jpg|thumb|[[Hypocaust]] in [[Saint-Rémy-de-Provence]], France]]
A [[hypocaust]] was an ancient Roman system of [[underfloor heating]], used to heat buildings with hot air. The Roman architect Vitruvius, writing about the end of the 1st century BC, attributes their invention to [[Sergius Orata]]. Many remains of Roman hypocausts have survived throughout Europe, western Asia, and northern Africa. The hypocaust was an invention which improved the hygiene and living conditions of citizens, and was a forerunner of modern [[central heating]].

Hypocausts were used for heating hot baths (''[[thermae]]''), houses and other buildings, whether public or private. The floor was raised above the ground by pillars, called [[pilae stacks]], with a layer of tiles, then a layer of concrete, then another of tiles on top; and spaces were left inside the walls so that hot air and smoke from the [[Furnace (house heating)|furnace]] would pass through these enclosed areas and out of flues in the roof, thereby heating but not polluting the interior of the room.

=== Roman roofs ===
{{further|List of ancient Greek and Roman roofs}}
[[File:Temple of echo Baiae.JPG|thumb|upright|Inside the "Temple of Mercury" at [[Baiae]], a [[Frigidarium|swimming pool]] for a [[Roman bath]], dating to the late [[Roman Republic]],<ref>"[https://www.britannica.com/topic/Temple-of-Mercury Baiae, historic site, Italy]". ''[[Encyclopedia Britannica]]''. Accessed 6 June 2021.</ref> and containing one of the [[List of Roman domes|largest domes]] in the world before the building of the [[Pantheon, Rome|Pantheon]]]]

In [[Magna Graecia]] truss roofs presumably appeared as early as 550 BC.{{sfn|Hodge|1960|pp=38–44}} Their potential was fully realized in the Roman period, which saw trussed roofs over 30 meters wide spanning the rectangular spaces of monumental public buildings such as [[Roman temple|temples]], [[basilica]]s, and later churches. Such spans were three times as wide as the widest prop-and-lintel roofs and only surpassed by the largest [[List of Roman domes|Roman domes]].{{sfn|Ulrich|2007|pp=148f.}}

The largest [[truss roof]] by span of ancient Rome covered the [[Flavian Palace|Aula Regia]] (throne room) built for emperor [[Domitian]] (81–96&nbsp;AD) on the [[Palatine Hill]], Rome. The timber truss roof had a width of 31.67&nbsp;m, slightly surpassing the postulated limit of 30&nbsp;m for Roman roof constructions. Tie-beam trusses allowed for much larger spans than the older prop-and-lintel system and even concrete vaulting. Nine out of the ten largest rectangular spaces in Roman architecture were bridged this way, the only exception being the groin vaulted [[Basilica of Maxentius]].{{sfn|Ulrich|2007|pp=148f.}}

=== Spiral stairs ===
{{further|List of ancient spiral stairs}}
The [[Stairway#Spiral and helical stairs|spiral stair]] is a type of [[stairway]] which, due to its complex [[helix|helical]] structure, was introduced relatively late into architecture. Although the oldest example dates to the 5th century BC,{{sfn|Beckmann|2002}} it was only in the wake of the influential design of [[Trajan's Column]] that this space-saving new type permanently caught hold in Roman architecture.{{sfn|Beckmann|2002|pp=353–356}}

Apart from the [[triumphal column]]s in the imperial cities of [[Rome]] and [[Constantinople]], other types of buildings such as [[Roman temple|temples]], [[thermae]], [[basilica]]s and tombs were also fitted with spiral stairways.{{sfn|Beckmann|2002|pp=353–356}} Their notable absence in the towers of the [[Aurelian Wall]] indicates that although used in [[medieval castle]]s, they did not yet figure prominently in [[Roman military engineering]].{{sfn|Beckmann|2002|pp=353–356}} By [[late antiquity]], separate stair towers were constructed adjacent to the main buildings, as in the [[Basilica of San Vitale]].

The construction of spiral stairs passed on both to [[Church architecture|Christian]] and [[Islamic architecture]].