How long would it take for nature to reclaim a completely abandoned city?

Question

Setting is late antiquity/early medieval with Mediterranean climate, abandoned all at once due to religious reasons. If i plan to have a character re-discover it a thousand years later, will it be recognizable as having once been a city? Is there any chance that some of the farmed crops might still grow on their own?

Answer 1

When we speak of Mediterranean climate, the archetypal location is of course the Mediterranean Sea.

The shores of the Mediterranean and of the Black Sea are positively full of ruins (or sometimes not-ruins) of ancient cities. One can hardly go more than a few miles without coming upon a site of ancient habitation. The vast majority of cities, towns and fishing villages have histories going back more than two millennia.

Most of these sites have been continuously inhabited, but some ancient towns or cities, or at least parts of them, had indeed been abandoned because of barbarian conquest, or because changes in religion, or because dramatic climate changes had made the site barely habitable, or because the changes in sea level had made the ancient ports unusable and quite often placed them way inland.

The viewer will notice in the photos included for illustration that everything which was not made of stone (and very occasionnaly of high quality Roman brick) is gone without a trace. Stone has a sporting chance to endure, especially if the abandoned city happens to be in a place where there is stone aplenty and nobody has any incentive to reuse the ancient stones. But wood would have been repurposed, reused and recycled in the blink of an eye.

As for farmed crops growing on their own, in the case of plants we speak of escape from cultivation and naturalization, and in the case of animals we speak of feral populations.

• The prototypical Mediterranean species of plants which occur just about all around the Middle Sea both in cultivation and living free on their own are the olive tree (which has escaped from cultivation so long ago that we cannot even figure out where it came from), the sweet chestnut, and the walnut (which came originally from Persia).

  Even the grapevine grows wild in many places around the Mediterranean, so that we don't even know where it came from originally.

• As for feral animals, pigs, sheep, and especially goats are well-known for being perfectly able to take care of themselves and to prosper and multiply whenever they are given the opportunity.

  For fun, consider the Cretan wild goats, which for a long time were believed to be subspecies of the true wild goat. More careful considerations have shown that the population is actually descended from domestic goats who had become feral some 3,000 years ago, after the fall of the Mycenaean civilization.

^{I cannot be sure, but I have a suspicion that the question might be asking if a field sown with wheat or something can continue producing wheat etc. without human care. No, it cannot. One isolated plant here and there, yes. Entire fields of grasses with edible seeds, no way.}

^{The Lions Gate of Mycenae. Mycenae was abandoned at some point after 1200 BCE; it remained perfectly recognizable as a city, with walls and gates, and one thousand years later it became a tourist attraction for the citizens of the Roman empire. Then civilization fell, lights went out, the tourist trap was abandoned; but another thousand years later the ruins of the three thousand years old city became a tourist attraction again. Photograph by Andy Hay, available on Wikimedia under the Creative Commons Attribution 2.0 Generic license.}

^{The religious complex of the Valley of Temples in Agrigentum was abandoned when the ancient Greek religion was itself abandoned in the late Antiquity. (Note that the Valley of the Temples is actually a rocky ridge and not a valley.) This particular temple, which is conventionally called the Temple of Concord, continued to be used for religious purposes until the High Middle Ages, just dedicated to another God. Photograph by user Ludvig14, available on Wikimedia under the Creative Commons Attribution-Share Alike 4.0 International license.}

^{The Krak des Chevaliers was abandoned in the 13th century, some 750 years ago, after being conquered by Baibars, the Mamluk Sultan of Egypt. It remained usable throughout this time, and was actually used sporadically to house small garrisons. Photograph by Gruppo Archeologico Romano, available on Wikimedia under the Creative Commons Attribution-Share Alike 4.0 International license.}

^{Arch of Roman emperor Lucius Septimius Severus (ruled from 193 to 211 CE) in Leptis Magna, the well preserved ancient city along the Mediterranean Sea, located 120 km Est of Tripoli, Libya. The city was mostly abandoned in the 7th century, and the tiny fishing village that had remained was fully abandoned in the 10th century, some 1,100 years ago. The ruins were then covered by sand dunes, and were rediscovered in the 19th century. The level of the sandy soil prior to the archeological excavation is visible. And yes, that's a 1,800 years old Roman road. Photograph by Luca Galuzzi, available on Wikimedia under the Creative Commons Attribution-Share Alike 2.5 Generic license.}

^{The beautifully preserved hexagonal basin of the ancient Roman port of Ostia is nowadays 1 mile (1.7 km) inland. The locals call it the Lago Traiano, Trajan's Lake. Photograph by Ra Boe, available on Wikimedia under the Creative Commons Attribution-Share Alike 3.0 Unported license.}

Answer 2

Stone and clay buildings will be visible for 1000 years or so, after that, it slowly becomes a mound. Stone and clay buildings will be visible and recognizable for centuries, but will slowly get buried. They will survive thousands of years more under the ground. Wooden buildings will last at most a century or two, unless used for fire first. Metal bits will immediately get pillaged and used elsewhere, unless hidden underground.

1000-year look Look above the excavated city area in the photo, at the foot of the hill. The walls of stone buildings are partially covered with soil, but it is still recognizable as a site. This is from Sagalassos.

Sagalassos, a typical example, was known to villagers in the 18th century, a thousand years after it was abandoned, and its name was decipherable to a traveller. Quite a few of the ruins of ancient Greek cities in Anatolia were known to local villagers in the 19th century, about 1000 to 1500 years after they were abandoned. (Wikipedia article in the links.) See the top part of the ruins, the obvious middle part is already excavated by archaeologists

A couple more pre-excavation photos, showing what a city looks like after 1000 years of abandonment in the Mediterranean climate:

https://www.alamy.com/stock-photo-ancient-city-of-sagalassos-in-anatolia-turkey-126413108.html

https://www.alamy.com/stock-photo-ancient-city-of-sagalassos-in-anatolia-turkey-126413148.html

8000-year look There is a settlement abandoned over 8,000 years ago, called "Çatalhöyük". You can find the Wikipedia article in the links below. This is what it looked like in 1958, before excavation:

It is basically a mound - barely recognizable. Despite this look, locals knew that there was an abundance of idols and statues in the area, and Mellaart (the archaeologist) was able to locate it. More info here: https://www.catalhoyuk.com/project/history Also, here is an article about how Mellaart was able to locate this site: https://library.biblicalarchaeology.org/article/discovering-catalhoyuk/

Another 1000-or-so year example

Finally, here is what the stadium in Magnesia looks like when two thousand years pass, before and after excavation: https://twistedsifter.com/2021/06/before-after-ancient-greek-stadium-excavation-utkrey/

This is a great way to visualize how the a stone structure looks after being covered with soil and dirt after 1000-1500 years.

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https://en.wikipedia.org/wiki/Sagalassos

https://en.wikipedia.org/wiki/%C3%87atalh%C3%B6y%C3%BCk

https://library.biblicalarchaeology.org/images/bsao080301900ljpg/

Answer 3

Location, location, location

It seems plausible that a city could remain recognizable as such after a 1000 years, depending on building materials and location. For materials, Stone is good, wood is bad. Brick not great. For location, dry is good, next to water bad, higher elevation good, valleys bad. On a stone bluff above the ocean could be good - Higher winds make it hard for plants to grow.

Answer 4

I can't see this part of the question really addressed in existing answers:

Is there any chance that some of the farmed crops might still grow on their own?

Yes, there'll likely be farmed crops still growing, however almost sure they'll not form plantations and it'd be very difficult / impossible to identify them as former crops without extended research.

Over that time crops would most likely adapt to wild conditions (better competition with other crops, adaptation to arid conditions if they were irrigated before; these will likely come with smaller and less yield). Also any plantation / homogenous population will be diluted and mix of different plants found.

Answer 5

A 1000 years later? Sure it would be recognizable. A Mediterranean-ish city from the late Antiquity or early Medieval period would likely be made out of stone and ceramic bricks/tiles, which can last much, much longer than that. Most buildings would at lest partially collapse, especially roofs (since roof beams were usually wood).

Note, we have examples of WOODEN buildings that could last 800-1000 years, if they were made of resin-saturated pine, or tar-soaked oak etc. Charred wood, especially cedar, can last almost as long.

As long as the city is not dismantled for building materials, or flooded, it will be recognizable as ruins for easily ten centuries if not more.