After the fall of the lizard empire, most of the lizard people fled to Node to avoid genocide (This is in the Lovecraft universe, racism is mandatory). In short order, this former bomb shelter became the permanent residence for the refugees.
So, Node is an awesome place. Since its designers couldn't really get rid of the supporting pillars, they decided to exploit them as much as possible. Some residential areas are built around pillars. Some are also statues, depicting Yig/Jormungandr/Apep or just a regular constrictor.
Other than that, the pillars are also used as nodes in the city's transportation system. The interconnected spider's web of bridges, safety nets, and the rails of the sky tram ensure that there's enough change in the surroundings for people to not feel trapped. Plus, there's a lot of vegetation.
These, however, are also problems.
Obviously, humans would probably want to properly finish the job. Even if they don't commit a total genocide, they would probably want to destroy Node. Lizard people are low in number and the Automated Security Forces of Node were destroyed during the war, along with the factories that made them.
Thus, Node can only hide and pray to Yig that the day, when Delapore and his cat, Niggerman, find the city, would never come. But just how can you hide away the life signs of an entire city? The transit system, lighting, filtration, waste-processing, and agriculture require a lot of things. Air, large reactors, lots of water, and so on.
While it's true that Node is connected to a system of underground railways and shelters, using them to lessen the load of the city's systems could actually make it easier to detect and would turn maintenance into a nightmare.
Humans don't fully understand the technology of lizard people, but even 2-1 IQ barbarian knows what a turbine sounds like or if a computer is turned on, not to mention what happens if they run into the maintenance crew.
Humanity has at around late-medieval technology, but they have magic to leverage that. In practice, this means they can bust down any door, given enough time. The only thing, magic can't do, is information gathering, thanks to Mephistopheles still operating the planet-wide network that spoils the packages of intel spells with false information and AI-upscaled episodes of Boku no Pico.
So, to ask again, how can you hide away the life-signs of an entire city?