Editing Trajan's Column (section)

== Spiral stair ==
{{See also|List of ancient spiral stairs}}
[[File:Trajans-Column-lower-animated.svg|thumb|upright|Section view of the pedestal and the interior stairway (click on image)]]

The interior of Trajan's Column is hollow: entered by a small doorway at one side of the base, a spiral stair of 185 steps gives access to the platform above, having offered the visitor in antiquity a view over the surrounding Trajan's forum; 43 window slits illuminate the ascent.<ref>{{harvnb|Bennett|1997|p=158}}</ref>

The column stands {{convert|38.4|m|1|abbr=on}} high from the ground to the top of the statue base:<ref name="Lancaster 419">{{harvnb|Lancaster|1999|p=419}}</ref> Located immediately next to the large [[Basilica Ulpia]], it had to be constructed sufficiently tall in order to function as a vantage point and to maintain its own visual impact on the forum.<ref>{{harvnb|Jones|1993|p=27}}</ref> The column proper, that is the shaft without the pedestal, the statue and its base, is {{convert|29.76|m|ft|2|abbr=off}} high, a number which almost corresponds to 100 [[Ancient Roman units of measurement|Roman feet]]; beginning slightly above the bottom of the base, the helical staircase inside measures a mere {{convert|8|cm|0|abbr=on}} less.<ref>{{harvnb|Jones|1993|p=28}}</ref>

The column is composed of 29 blocks of [[Carrara marble|Luni marble]], weighing in total more than 1100&nbsp;t.<ref name="Lancaster 419"/> The spiral stair itself was carved out of 19 blocks, with a full turn every 14 steps; this arrangement required a more complex geometry than the more usual alternatives of 12 or 16.<ref>{{harvnb|Jones|1993|pp=31–32, Fig. 9}}</ref> The quality of the craftsmanship was such that the staircase is practically even, and the joints between the huge blocks still fit accurately.<ref name="Jones 31">{{harvnb|Jones|1993|p=31}}</ref> Despite numerous earthquakes in the past, the column today leans at an angle of less than half a degree.<ref name="Jones 31"/>

Trajan's Column, especially its helical stairway design, exerted a considerable influence on subsequent [[Roman architecture]]. While spiral stairs were before still a rare sight in Roman buildings, this space-saving form henceforth spread gradually throughout the empire.<ref>{{harvnb|Beckmann|2002|pp=353–356}}</ref> Apart from the practical advantages it offered, the design also became closely associated with imperial power, being later adopted by Trajan's successors [[Antoninus Pius]] and [[Marcus Aurelius]]. In [[Napoleon]]'s time, a similar column decorated with a spiral of relief sculpture was erected in the [[Place Vendôme]] in Paris to commemorate his victory at [[Battle of Austerlitz|Austerlitz]].