PutOption 1: super-large tensile support structures
It may be possible to distribute tension through specially designed structures. If the dome is high enough then the ceiling's weight may be offloaded to side columns.
https://www.hisour.com/history-of-modern-period-domes-32124/
But this solution doesn't properly communicate the sheer awesomeness of the Lizard people. Therefore...
Option 2: Put the pillars outside. Inverted. And falling towards the sky.
The Lizard scientists are really, really crafty. They anchored what would eventually be the roof of Node to extremely resilient tethers, and tied these to a captured asteroid placed in orbit - now a ballast to an inverted support system.
As a bonus, they gained a space elevator. Cheap space exploration, anyone?
