Concrete Igloo or Vault

For years I have been thinking of how to build a mold or a couple of different molds   that I could poor concrete into  where I could make one or two pieces a day  for a few months  to get enough parts to be able to stack together like an IGLOO for a dome or as a VAULT .    I have seen Igloos made from Styrofoam parts   but a concrete igloo would be much more durable.   Sometimes I think of a Soccer Ball for parts of a sphere but there must be more ways to build a dome.... Such as Orange slices  of an orange fruit that has been cut in half.
Anyone else ever think of this ?   I would like a way for the pieces to if not  lock together , at least a ledge that helps reinforce the next  row.   You would never want to be in  a concrete igloo when it collapses!   How to make it strong ?    We know how the Romans used stones to build arches and bridges etc.

Neat idea, I love building methods that can be done incrementally.
To minimize the number of molds needed and the side of the pieces, maybe try this kind of dome:

https://www.domerama.com/calculators/trapezium/

This is like the orange slices.
To figure the dimensions of a block rather than a flat panel, calculate an inner and an outer dome and the distance between the two.

I think styrofoam blocks skinned in netting and plastered with cement could be a good option.

Concrete made with Styrofoam could also be good:
https://permies.com/t/271989/Good-yt-video-increase-knowledge

Adobe blocks are free, but they do requires attention to detail that I myself don't think I could mister
Cast soilcrete blocks might be the best option in terms of materials required vs skill level.

Scott, where are you located, it helps understand your needs a bit.
Concrete blocks can be cast, you need he skills of a stone mason or strong mathematics.
As William suggested adobe is straight forward, the material id free but the end product is not
it takes a lot to create adobe bricks.
Creating the dome based on a circle is covered in much literature but essentially you start with a foundation, a centre pole and a bit of string.
The bricks are laid around the pole using the string as a guide.
Other techniques are used to create the actual dome shape you want.

I can’t find the video now, but I watched one a long time ago about a farmer that built an under ground dome house just like building a cob bread oven. He built a big mound of dirt, covered it with old tarps, then built a rebar frame and poured stiff concrete. When set, he dig out the dirt and used it to bury the dome.