Floor plan unknown symbol breakthrough

There are still formerly planned floor or ceiling openings. The duct ventilation of the bathroom on the upper floor could therefore fit, that this pipe continues into a possibly existing basement? Are the thin walls around the openings present or only planned and never executed?

There remain former planned floor or ceiling openings nonetheless.
Ventilation duct of the bathroom on the upper floor could therefore fit, that this line continues into a possibly existing basement?
Are the thin walls around the openings present or only planned and never executed?

The opening is present. Indeed, it could be a planning of the chimney. However, this was not carried out. There is nothing of this kind visible on the wall or on the ceiling.

The fireplace is in the living area and there was an open fireplace with a bench installed there.

Ah yes, circle was a chimney flue :)

I'm Bad bottom right is the chimney (counterpart living room ground floor)

And in the children's room the counterpart of the dining room.

I am attaching the overall floor plan again.

Basement would also be interesting. It could be the drain that runs from bottom to top with its ventilation.

On the roof ridge there is approximately at this point a pipe that regulates the air supply for the sanitary facilities.

Ah yes, circle was a chimney :)

And in the children's room the counterpart of the dining room.

Basement would also be interesting.
It could be the drain that runs from bottom to top with its ventilation.

I just checked again.
It appears to be the ventilation pipe that runs from the basement up to the attic. You can hear the hollow space when tapping. However, this is not in the corner, but somewhat more central in the wall.

This will unfortunately make the breakthrough quite difficult.

Thank you very much, everyone!

Then I will solve the puzzle. The symbol means: Rauchfang. It is the funnel-shaped area above the fire in open fireplaces, where the smoke is collected (hence the name) and then led to the chimney. At the end (see 1. OG) it is therefore nothing other than a chimney. The marking in the living room (so round) is formally also a "Rauchfang", but a round one.

Google is also such a patient thing (sentence is only for the necessary 5 words)