Some parts of the walls are Roman, that curious thirteen-sided building called the Multangular tower forming part of it, and also the lower part of the wall leading from this tower to Bootham Bar, the upper part being of later origin.
"Vanishing England"
P. H. Ditchfield
The round, the triangular, the square, and Multangular column, is indifferently raised over the grave of a Chinese; but the most common form of a monument to the remains of persons of rank consists in three terraces, one above another, inclosed by circular walls.
"Travels in China, Containing Descriptions, Observations, and Comparisons, Made and Collected in the Course of a Short Residence at the Imperial Palace of Yuen-Min-Yuen, and on a Subsequent Journey through the Country from Pekin to Canton"
John Barrow
Parts of the Roman walls can still be traced, especially at the so-called Multangular Tower.
"The Romanization of Roman Britain"
F. Haverfield