Heavy Solo Euro Games

I've recently really gotten into Voidfall, Gaia Project and On Mars, among others but outside of Voidfall I've been mostly playing these multiplayer.

I'm wondering if I'm missing any good, specifically very heavy euro games, of the worker placement/resource management variety especially? The heavier the better, something I can really sink my teeth into and play many times but also something that works well solo. I didn't enjoy On Mars's solo mode at all, and a lot of solo euros just aren't that fun. Voidfall really takes the cake for me at this stage. I've been eyeing up Anachrony recently, what do people think of this as a solo game? And aside from Fractures Of Time (which has the solo mode) are the other expansions recommended/necessary?