I think the TV event is located at the tip-top of the orange building, where the roof takes up a good bit of the screen. There is a black(?) crystal that erratically moves around in that area, and teleports you to the TV. I could totally be forgetting about something considering that this is one of the few events in this game that I haven't reached in any of my playthroughs.
But the orange building has been redesigned (it's the flying fish world now, isn't it?), and I think that rooftop area has been removed.
Correct. It's flying fish world, and the giant TV event is now either unaccesible or completely removed.
Hmm. You used to be able to still access both the orange buildings and fish buildings in some of the versions. I hadn't bothered to play the most recent version of the game, but from what I recall, the orange buildings and TV event are still in the data.
Okay, thanks to the Yume 2kki wiki, I found out that the old orange building complex is still accessible (although there's no teleporter on the rooftop, or it could be a random event, I'll check it out again soon).
To access the old concrete world, go to the (seemingly) empty one from the highway tunnel, then equip the fairy effect and wander around. A flashing teleporter will appear, and it will take you to the old concrete world.