Mushroom expert is updated much more frequently. Local field guides are good for getting a general idea of what you’re looking for out there. But if you want to know exactly what you’ve found, running through the whole process on mushroom expert will give you a positive ID. The local mushroom hunters I learned from told me to not trust books as they are almost always out of date in some way.
Now that you mention it, I seem to remember Xenophon stumbling across giant ruins that perplexed him while out on campaign. I think they were Persian? It very much could be drawing on the experiences of people seeing the ruins of fallen empires.
Edit: AI is telling me that Xenophon traveled through the impressive ruins of Assyrian cities, he was fighting the Persians.