There are thousands of interpretations of the Underworld out there, but they all appear to have died as a reoccurring theme, to say the least.
Technically speaking you can’t speak about the Underworld without mentioning death so it does make sense, which is why experts were quickly able to spot the fact that the tunnel from the pyramid of Teotihuacan from Mexico was meant to be a direct representation of a descent into the underworld.
The tunnel is quite big, to say the least as the experts weren’t even able to record how deep it truly goes since the further you go the less air you get and you essentially end up just dying before you’re even close to reaching the end.
There are plenty of carvings and texts on the walls which all refer to this as the tunnel to the Underworld. The tunnel was originally discovered 19 meters or 33 feet underneath the ground level and as far as we know it is the second-largest structure that we’ve ever come across at this site, to begin with.
For the most part, experts believed that the priests here would oftentimes sacrifice animals and plants. The tunnel was abandoned by 550 AD and it supposedly was inhabited by over 125,000 people. Nobody knows why they left their tunnel but many believe that the lack of oxygen could have been too much for a lot of them.