Archaeology in the city of Rome, although complicated by the continuous occupation of the site, is blessed with a multiplicity of source material. Numerous buildings have remained above ground since antiquity, such as the Pantheon, Trajan's Column, temples and honorific arches, while extensive remains below street level have been excavated and left on display. Nearly 13 miles (19 kilometers) of city wall dating to the third century ce, and the arcades of several aqueducts are also still standing. The city appears in ancient texts, in thousands of references to streets, alleys, squares, fountains, groves, temples, shrines, gates, arches, public and private monuments and buildings, and other toponyms. Visual records of the city and its archaeology can be found in fragmentary ancient, medieval, and early modern paintings, in the maps, plans, drawings, and sketches made by architects and artists from the fourteenth century onwards, and in images captured by the early photographers of Rome. Textual references to the city are collected together and commented upon in topographical dictionaries, from Henri Jordan's Topographie der