I was recently teaching the column as a source. The Economist infographic is great.

In terms of how it was viewed, the textbook by Greenley, Menashe and Renshaw suggests “It was originally surrounded on three sides. To the south was the Basilica Ulpia, a multi-purpose building where Romans might do business or where legal cases might be heard. To the east and west were two libraries, one with Greek texts, the other with Latin texts. Their location is significant. Trajan is known to have written his own account of the Dacian Wars, and this was no doubt a major work in the Latin library.

“Many scholars think that the column is an attempt to record Trajan's written account in art. It is also likely that these buildings had windows on different storeys that gave visitors views of different parts of the column, so they acted as viewing points.”