Do you recall the backyard being emptied of dirt?
That was to go down one flight to create a parking garage in the cellar.
You can see the ramp down at the very top of the next photo.
But now they are going up.
That first floor framework is temporary.
They will pour concrete on top and then take it out after the concrete has hardened.
The round tanks are for draining the swimming pool for maintenance.
Get ready for one helluva concrete pour.