Doors are always full of unknowns, and far too often it’s a gateway into another world. Every door that you open up for the first time is a surprise, a world that you’ve never seen before. Everywhere you go, doors are meant to be opened, with the exception of this one — it’s meant to stay closed for a very good reason. While what’s behind this door by why.not? is curious enough to tease our imaginations, I’m actually more intrigued by the mysterious technique used to create the door arch at the top. It’s a puzzle worth solving more than what’s behind the door.
It looks like he (?) used the round arch technique, which was famously used by the Romans.
The main picture on the wikipedia page shows its construction: https://en.wikipedia.org/wiki/Arch
@flip, I agree with you. It looks to me that he used 1×2 plates, two 1×1 plates, and slope pieces with grooves.
One of those 1×1 has a clip which connects to a flexible tube.
@lessjunkfood, yes that makes sense.