The second Death Star's reactor core.

The Death Star wasn't completed yet. Maybe when it was finished, the shaft in his throne room would have been sealed.

 

thx Bib
like always u have plausible answers

 

I might be remembering incorrectly, but I think the RotJ novel accounts for the reactor shaft. It says the impromptu throne room set up for the Emperor's visit had previously been some sort of control center, and for whatever reason the shaft was left uncovered.

 

"Why is there a "Shaft" at all in the Throne room ??"

Because Palpatine likes to keep the heads of the Jedi he's killed as trophies. Mace Windu was his toughest opponent.

 

Lucas "placed" a shaft for this to happen, who cares that it is there for no reason, but that is a good question why does the Emperor need a shaft to the core? He doesn't inspect it, it is an Empire conspiracy I say.