Most of medieval Rome - meaning the populated district from, say, the 6th century to the 16th century lies within the Campo Marzio. Definitely a poor choice for habitation, because it's a flood plain embraced by a broad bend of the Tibur. In imperial times, the campo was a district for major public monuments and theaters - housing was for the most part located elsewhere. After the shift of the imperial administration to Constantinople in 330, Rome decayed and changed rapidly. In 398 the imperial government in absentia found it necessary to issue a proclamation prohibiting, under pain of exile, the building of hovels and huts amongst the once grand civic monuments of the Campo Marzio. In the end the huts and hovels won out as the dwindling population coalesced in the campo (population estimates calculate over 1,000,000 in the 1st century AD, crashing to less than 30,000 by the 6th century) There was a price to pay for that decision. Aqua Alta. High water. The Tibur periodically overflowed its banks, and numerous plaques (more than 100 remain) note the inundations, some unbelievably high. The earliest remaining plaque is from an inundation in 1277; some are fanciful and some are mundane, but they all tell a story of water washing over the habito.
high water mark of 1422, facade of Santa Maria Sopra Minerva
high water mark of 1530, facade of Santa Maria Sopra Minerva
high water mark of 1597, facade of Sant' Eustachio
Rising flood waters are on our minds these days. Oh sure, the North Carolina legislature has tried to make the problem go away by officially banning mention of rising sea levels due to global warming in documents and planning projections funded with state money, but cities from New York to London to Venezia are preparing for the inevitable. Wandering the narrow streets of Roma, as I so often do, I began to wonder: If the water rose to such unbelievable heights in the 15th and even 20th centuries (before the protective embankments were built in the 19th century, and upstream dams in the 1950's and 60's), what does the future hold? Here is a video of an urban intervention I did of a possible scenario: