If I could recreate anything from history-

If I could recreate anything from history, it would be the Library of Alexandria. Lost in that great fire were mathematical proofs that rival anything in today's computer age, engineering secrets that enabled builders to construct buildings that have stood for centuries, metallurgy secrets such as the tempering of copper, medical breakthroughs that even today could have saved countless lives. The dark ages...roughly 1000 years of stagnated progress for humanity may never have occurred, had this knowledge been available.

All burned in 48 BCE.

https://history.stackexchange.com/questions/677/what-knowledge-may-have-been-lost-at-the-library-of-alexandria

Probably just a bunch of scrolls explaining how to make a sword or a nice recipe for meat pies.
Just because the place burned down doesn't mean the information it contained would have been erased from the people's memory.
If it was important they would have rewritten what they knew.

@mchill said
If I could recreate anything from history, it would be the Library of Alexandria. Lost in that great fire were mathematical proofs that rival anything in today's computer age, engineering secrets that enabled builders to construct buildings that have stood for centuries, metallurgy secrets such as the tempering of copper, medical breakthroughs that even today could have saved ...[text shortened]... story.stackexchange.com/questions/677/what-knowledge-may-have-been-lost-at-the-library-of-alexandria

Hanging Gardens of Babylon

That would be good to visit, but by the time a tourist shop and a bar had been added...

These suggestions are fabulous but in all honesty I'd rather go back 1997 and convince my young 17-year-old ass to invest in Amazon. It's working out well for Ol Jeffrey Boy! Plus, I like air conditioning and central heat and the rest of those amenities we are privileged to have. Fast cars and fast women!

The Giza Plateau.

In all it’s finery, the pyramids in their original glory, with access of course. Also with the Nile flowing in its place of that era, which I believe was quite close by.

Must have been magnificent.

The Crucification, so I could tell the Romans that nailing the dude to a cross isn't going to put an end to it, that his followers are just gunna keep going on and on about it, and there will be wars and crusades coz no-one is ever going to agree, and they'd be better off just putting the kettle on and having a nice cup of tea together.

@mchill said
If I could recreate anything from history, it would be

Life before covid.

@folly said
The Crucification, so I could tell the Romans that nailing the dude to a cross isn't going to put an end to it, that his followers are just gunna keep going on and on about it, and there will be wars and crusades coz no-one is ever going to agree, and they'd be better off just putting the kettle on and having a nice cup of tea together.