Allagan Technological level, architecture?

[Risvertasashi]

Well, in pragmatic terms... Allagans had spaceships, cloning & bio-engineering technology, nanotechnology, sapient AI, and technology that met all their energy needs (post-scarcity in at least one aspect). They're pretty much as high scifi and scifi gets. They're way above what Battlestar Galactica had. Star Trek perhaps a bit closer, but they only touched on transhumanism as an occasional episodic content. Redshirts, once dead, were pretty much... dead. So you can make a case for the Allagans being beyond even that. Perhaps somewhere between Star Trek and Culture, though certainly on a much smaller scale than the latter.

I can't think of any examples that are actually between those 2 off the top of my head, though.

[Fenral]

Doga and Unei mentioned that the completion of the Syrcus Tower was not only the apex of their civilization, but also the start of a few hundred years of decline in which a bunch of the empire and its technology fell to ruin. I'm thinking there's a possibility that any Allagans that didn't end up on the CT energy grid (i.e. those in space) could have kept developing independently of their earthbound brethren, in which case there could be some Vorlon-tier offshoot out there wondering what the hell happened back on Hydaelin.

They were also just as, if not more, guilty than the Garleans in pirating tech from precursor civilizations, so I think the idea of Ascians having a hand in reviving Xande, at the very least, is not totally beyond consideration. We only got that story from the perspective of those on the outside, after all.

[Shadygrove]

Those roads may bear those names - but may not have been built by the Allagans themselves - they may have been built by civilisations that came later, in an effort of trying to recapure some of the Allagan glory by naming the roads thusly.

If you want a real life example, you only need to look back to the height of the Roman Empire.

If you want a real life example you needn't look any further than El Camino Real in California.

Been a long time since it was named. Nothing of the original dirt path remains. But the name does.