The complex seems to be a building made (or owned) by a company named "Commodore". The underground seems to have been modified into a huge bunker. In the parking lot there's a crashed car with a plastic catfish (it's important for later)

At the entrance of the building, on a table, there are tickets for random places in italian. Nothing else in the map gives any clues on location so it's probably an asset thing and not related to lore. (Unless stated otherwise! But, as an italian myself, i have to say that usually the government wouldn't do anything with it and instead turn it in an overly-priced tourist trap as usual).

A giant plant seems to have grown deep undeground (It crashed there like a meteorite?). By the leaves, it looks to be a member of Crassulaceae, though it might be simple convergent evolution. At the base of this plant is deep-blue liquid. The plant has seemingly god-like powers to an extent, as its grown has caused rifts to open and strange minerals to form in nearby caves. When entering a rift, you swim in a tunnel made of those strange minerals. The liquid also seems to be the same.

A room attached to one of the dimensional branches is clearly made for interviews, which means two things: 1) the appearance of the plant was sudden and actually "took" a pre-existing room, maybe from a -1 floor, that existed before, who knows; 2) The appearance wasn't sudden and the world knows of it, perhaps Commodore is using it for money/status/research to an extent. In the bunker (near a rift) there is a room with parking lines, likely a room for trucks to deliver things and people. This, along the easy access to the bunker, further proves the second point of my theory. What's even more interesting is that there are guns and bullets scattered around the bunker: a fight ensued and we don't know who or what attacked. And where are corpses? Did they drop everything and run away? Or were the corpses stolen?

One of the portals leads, through a pink interdimensional bridge, to a medieval looking building (a castle, I presume) : it's basically a square with a garden (kind of, dunno how to call it ) in the middle of it. It's seemingly in use up until recently since it's already armed with furnitures and paintings. On the left is an area that seems to be a church of sorts (THE TRIANGULAR MOTIVE OF gm_Stratos IS ON THE WALL!?), while on the right is a theater area with many tables and chairs. In this area you can find another plastic catfish (who leaves them behind?).

Going forward and taking a few steps on some diamond-shaped structures, you reach a downard portal that leads to a white plant, like the one in the bunker. There was yet another plastic-looking catfish, so I placed it in the water and a counter appeared: 1/5, though it said "3/5" - probably a bug. (The portal to go back is behind the plant)

I placed another catfish (2/5). A text informs me that "Wormholes begin to appear". Those things appear as small, glowing lights and bring you to a dark-blue tunnel placed between a white branch and a dark-blue branch. They seem to be teleporters: white lights function as entrance, blue lights function as exit

I placed the other catfish (3/5) but nothing happened and the counter didn't go up.

I found a fourth catfish (4/5) in the area with blue-red-green lights: it's between two barrels and a panel on the wall. Again, nothing happened. Off i go to find the damn fifth catfish emerald... man, i hate when mappers do this.

The last catfish is on the second floor (the dark one), behind the chairs and plant (5/5). I brought it to the white plant's water and... nothing happened. Did i miss something? I then tried to brute force the secret event but i couldn't... so I just wasted a couple hours, cool.

Anyway, discover the secret and have extra fun for me. This map is awesome and i loved exploring it. Lastly, I HAVE to praise the creativity since we don't have many "Mythical plants that screw up the multiverse" kind of scenarios.