Ok so I have deconstructed it and find a way to build it that is methodical and can be easily understandable
so first of all, you have to extend the sandstone pillars with these
two double stone slabs and two stone brick blocks.
and then extend the upper stone brick blocks to create an overhang, such as this
and then you can start making a base pillar to the top of the sandstone pillar
but on the upper stone brick where you have that overhang, you would want to put the upside down stairs there as well
creating something like this in the end
on both end it became like this
let's see the old arch, it has the same shape now
as you were building that anvil-shaped thingie you will notice that you are intersecting some section of the izack columns, you would want to do this to them
destroy the cornermost upside down stair from the izack column intersecting the arch and exchange it with the stone brick
and now the upside down stairs should be connected to each other.
continuing on the arches, put down a stone brick atop the anvil's overhang
and extend them all across like this
but this time stop the upside down stairs just before the middle block gap
and the going to the last layer first off you build a connecting bridge between the two structures you just made
and then continue to extend the blocks atop the upside downstairs and then put another layer of upside down stairs and here's what you end up with
go inside under the arch and at the very top layer put an upside down stair heading outside
and it's finished
actually this is a very complicated and advanced derivative of a simple building technique I will call as the inverted pyramid, which by the name you would have guessed what it consists off.
To build an inverted pyramid, you just need to build the top end of a pillar, and then build layer and layer of upside down bricks until you met the height that satisfy you. and with this one, I break several repetitions to make it look better.
and by the way, a glimpse of Basilica Nostrum Domina Magna Scientiae Hypathia Mater Cognitionis (Basilica of our great lady of science, Hypathia mother of knowledge) A great temple of the probe dedicated to women of science, I'm planning it to be built in the eastern edge of the SkyCity
and at the back of the altar, replacing the usual sight of a cross, I put a likeness to the Holy Probe

even though I'm still bad at sculpting and don't know if it's like the Holy Probe at all :lol: