How many of these ruins go back that far though? I mean, for the Ayleid ruins the simple explanation for most of them is probably ‘the Nedes killed everyone there when St. Alessia rebelled.’ The Nedes got conquered by the Ayleids and the Yokudans. The Khajiit got decimated by plague. The Dwemer poofed themselves out of existence. The Falmer mostly got conquered by the Nords. Most of that was much closer to the present than the Dawn Era.

I don't think there's a universal reason for all the ruins, you have to look at them from at a case-by-case basis.

The Ayleid ruins in Cyrodiil should be obvious, while those in Valenwood became abandoned after their culture declined due to being assimilated into and simply outnumbered by the Bosmer.

Dwemer ruins should also be quite obvious.

The ruined Xanmeers dotting Black Marsh we know for a fact come from a time when the Saxhleel viewed Sithis as a destructive force and sought to fight against Change by creating stone structures, before Duskfall happened and their society went from opposing Change to embracing it.

The Direnni and Ayleids in High Rock were displaced by the emerging Bretons, leaving their ruins behind. Hammerfell's Yokudan ruins are mostly Necropolises, from what I recall, so not really places where people live anyway.

Morrowind's ruins are all from the time of Chimer Daedra worship, which is - to put it lightly - frowned upon by the Tribunal Temple.

Skyrim's ruins are similar, in that a lot of them are either literally tombs, or were built by and for the Dragon Cult in the Merethic, which is not exactly good vibes in the modern Eras. Saarthal is a notable exception, but we also know that excavation of it really only started in the 4th Era, while other "ancient" cities (notably Windhelm) are still inhabited to this day.

Benzux wrote: »

I don't think there's a universal reason for all the ruins, you have to look at them from at a case-by-case basis.

The Ayleid ruins in Cyrodiil should be obvious, while those in Valenwood became abandoned after their culture declined due to being assimilated into and simply outnumbered by the Bosmer.

Dwemer ruins should also be quite obvious.

The ruined Xanmeers dotting Black Marsh we know for a fact come from a time when the Saxhleel viewed Sithis as a destructive force and sought to fight against Change by creating stone structures, before Duskfall happened and their society went from opposing Change to embracing it.

The Direnni and Ayleids in High Rock were displaced by the emerging Bretons, leaving their ruins behind. Hammerfell's Yokudan ruins are mostly Necropolises, from what I recall, so not really places where people live anyway.

Morrowind's ruins are all from the time of Chimer Daedra worship, which is - to put it lightly - frowned upon by the Tribunal Temple.

Skyrim's ruins are similar, in that a lot of them are either literally tombs, or were built by and for the Dragon Cult in the Merethic, which is not exactly good vibes in the modern Eras. Saarthal is a notable exception, but we also know that excavation of it really only started in the 4th Era, while other "ancient" cities (notably Windhelm) are still inhabited to this day.

I agree with this. It's either because of extinction, decline, or cultural shift (like Xanmeer architecture - > mud structures). Another one to add to the above is Nedic ruins, we see a lot of them around Craglorn, and their civilization apparently declined and was assimilated to other cultures.

There isn't much erosion and inhabitants don't recycle or repurpose

You have to remember that even before ESO, there are thousands of years of history that precede us (well over four thousand). Maybe tens of thousands, since we can't guarantee that the historic dating is 100% accurate; plus, given the lack of linearity that the Dawn Era had, there's a lot that happened but that was before mortal civilizations rose up.

We also have to recall that no era had as much change and eventfulness as the Merethic and First Eras. Stories abut Pelinal Whitestrake's mysterious rise tell us that he'd raise up kingdoms and armies, only to abandon them and do it again. That account alone is enough to explain why there are so many ruins: countless cultures, kingdoms, empires and states have risen and fallen since the construction of Ada-mantia (Direnni Tower).

Plus, we have accounts of how civilizations like the Ayleids fell. In major cases like the Ayleids and the Dwemer, we know how they fell (albeit not all of the details, such as in the case of the Dwemer).

Additionally, regarding this "reset" concept you've brought up, you're not entirely wrong: the entirety of existence is in a cycle, the kalpic cycle, and the Dawn Era was effectively the chaos in between the previous kalpa and the new one. Prior to this kalpa, the world would cycle through events before being eaten by Alduin and reset into a new kalpa. The Nordic heroes of the first era defied this by using the power of an elder scroll to send Alduin forward in time, thus being the cause of the return of the dragons in Skyrim. If you've played Skyrim but haven't gotten far enough in the MQ, this is addressed and (SPOILER) you indefinitely postpone the cycle by defeating Alduin in Sovngarde.

However, as far as we're aware, this cycle effectively resets the entire world completely, meaning those ruins couldn't be remnants from the previous kalpa. However, this does raise an interesting question because we have knowledge of a few fragments of things that existed in previous kalpas. Lyg, for example, was said to have been destroyed by Mehrunes Dagon in a previous kalpa, meaning the Aedra and Daedra (or at least some of them) can survive the reset of the kalpic cycle. Umaril the Unfeathered's father is supposedly from the last kalpa. This means that either Umaril himself also comes from that kalpa, or he was ejected from the nonlinear chaos of the Dawn Era so he could live in the Merethic Era of this kalpa. This implies that it's not just the et'ada that can survive the cycle turning over, but also mer as well. This does tie in with the belief that the lost Aldmeris is simply a collective vision that the Aldmer had of the previous kalpa so it's entirely possible that the modern-day mer really are direct descendants of the inhabitants of the last kalpa. However, that doesn't mean that Ayleid civilization existed in the previous kalpa, as each kalpa is almost certainly different in the way that civilizations rise and fall.

What happened in the Dawn Era is honestly beyond what mortals can comprehend (and even we, outside of the lore, have trouble understanding its events due to the lack of linear time). Everything is destroyed between kalpas, yet some things seem to survive. It's a mystery that I doubt we'll ever have a complete answer to.