Servian Wall
The so-called Servian wall. Although the ancient sources state that this wall was built by king Servius Tullius in the sixth century, it is more plausible that it was in fact constructed after 375 BC. The stones, tufa from Veii, can not have been obtained before this city was captured. This pictures shows the largest surviving part of the wall; it is near Stazione Termini, which can be seen in the background. A satellite photo can be found here.
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