Unknown structure in 1920s house

[PeteMars]

Anyone have any idea what this faint bit of what looks like an arch might be, near corner of back wall and party wall in kitchen?

Also, how this half landing is being supported?

Finally, what's supporting the masonry (non load bearing) wall that's directly above the stairwell?

 

[freddiemercurystwin]

Who knows, pry some plaster/plasterboard off and you'll find out, only way to be sure. Despite what many think, old houses were often constructed out of crappy materials, low skilled workers, dubious building techniques and developers who were only interested in profits.

 

[Wayners]

Many stairs are supported at the top and bottom and everything in the middle is suspended.
Often the angle cuts off a room so you get boxing which is fixed to the stairs.
The stairs is holding the boxing.
The corner arch is covering cable or pipes maybe.
There was timber joist so the went under it encroaching in room corner

 

[PeteMars]

Many stairs are supported at the top and bottom and everything in the middle is suspended.
Often the angle cuts off a room so you get boxing which is fixed to the stairs.
The stairs is holding the boxing.
The corner arch is covering cable or pipes maybe.
There was timber joist so the went under it encroaching in room corner

Sorry I didn't quite understand your last sentence

 

[Wayners]

Timber joist runs along the top of wall or near it..
Years ago they never had drills so for some it was easier to put cable or pipes under joist. This ment that cables or gas pipes could be seen so they boxed in.
See all sorts of odd boxing in house.
Depends on age of you but originally is might not had any services so old cables and pipes put in at odd places...