This article contains spoilers for Mario Odyssey Edit
The Power Moons in Super Mario Odyssey are the goal of the game, with Mario having to collect them to power up to Odyssey and progress through the game to be able to catch up with Bowser. They are found in a multitude of Kingdoms around the Mushroom World, but are most notable used in New Donk City. They are claim to be the source of urban power by an NPC, and when Mario is commissioned to reclaim the underground NDC Power Station from Poison Piranha Plants, we see this to be very much true. This shows Power Moons are able to have their power harnessed to provide power to a city, but that begs the question of just how much power they hold.
We can look to the very same city, however, as Cappy reveals that the city itself built using the energy from Power Moons. This may seem at this point to indicate that the Power Moons simply were used to aid with construction, but post-game information reveals some interesting hints as to a different answer.
The three Moon Kingdoms of Odyssey reveal some interesting lore to the Mario series, such as life perhaps originating there:
"Interestingly, similar creatures can be found in the Seaside Kingdom. Did life on our planet (which began in the seas) actually originate on the moon?"
and Lunarian societies existing, with their own Goddess and architecture:
"Legends tell of a moon goddess, and this wedding hall is said to have been created in her honour, though no one knows for sure."
This seems very interesting for those interested in this side of the franchise, but as we delve deeper into the Moon's Kingdoms, we find out something quite peculiar about these Lunarians. In the Darker Side, we learn that Culmina Crater "was formed by a huge meteor collision long ago." It goes on to state:
The impact destroyed the civilisation that flourished on the moon, which is how Culmina Crater came to be. The crater itself is so massive, you cannot see the bottom.
Indeed, this was the main location of the Lunarians as it appeared to be here that their civilisation was destroyed. But why might they be found here? Well, this is where we find out a hint about NDC's origin. The crater appears to be at the location of a former city, as indicated by their town hall, the last standing building in this area. What's odd about this though, is it resembles the town hall found in NDC almost identical, noting:
This colossal building stands in Culmina Crater. If you look closely, it seems to resemble the city hall in New Donk City. Some think it's based on New Donk City Hall. According to researchers, it might be one of the remnants of the civilization that once flourished on the moon. But with little evidence, this theory lacks credibility."
However a caption expands upon the similarity with "The original? A copy? Who knows?", which shows it isn't proven to be based off the NDC and could in fact be the original. Due to NDC being created with energy of the Power Moons, and the Moon possessing such a building, there appears to be much more of a connection that it appears. Indeed, this implies that perhaps NDC was created by the Power Moons, as the Lunarians had access to those items as well (they are found in all three Moon kingdoms, after all). This would explain why the buildings are incidental, as they were created by the same thing. In fact, the Moon Cubes produce more Power Moons, and are shown to have originated from the Moon, implying that the Power Moons on the Mushroom World may have actually come from the Moon itself, which would further provide a connection.
However, a single building is not much of a good source. However, considering the Darker Side has a Warp Pipe leading to the lunar interior, there may have been survivors that seeked refuge underground. Why may this be important? Well, we see more of the Moon's interior in the other Moon Kingdoms, and one area in the Dark Side look particularly interesting.
It appears that there is an entire city located here, and one that looks very similar to NDC. In fact, this area appears extremely similar to an area found in NDC itself. These similarities to NDC imply that they could both share the same creator, which would be the Power Moons.
This would mean that the Power Moons are able to create an entire city, and so many of them should be able to scale up to City Level!
What does this mean for scalingEdit
Well, we see that the Mecha Wiggler absorbs the energy from NDC , which in turn means it is absorbing Power Moon energy, and so should itself be City Level (assuming it doesn't scale to Mario, anway)! Whilst it may not have as many Power Moons as NDC, the Odyssey is also empowered by many Power Moons, including quite a few Multi-Moons as well! This might mean it could have around City Level strength, which means when Bowser shoots down the Odyssey with his airship, or when Ruined Dragon shoots down the Completed Odyssey, they are actually doing quite powerful feats (although the latter one is more reliable. Plus, having City Level cannonballs would cause a revision of just how strong minor enemies (such as Koopas) are, and will likely result in it being outlier.). So, this is quite an interesting finding, although it should be kept in mind this is piecing together many hints throughout the game, and may not be what was intended. We can't say for sure, but this evidence appears to point towards this.