The Eiffel Tower fact I would have called bullshit on...but so it goes.
"Mammoths were alive when the Great Pyramid was being built." I guess I knew that, with Wrangel Island and all...but cool to consider.
So...your Time Machine awaits. 12 hours is all you get. Would you choose the Pyramid...or the Mammoths? Pyramid...hot. smelly. shouting. But...beer. Mammoths...cold. smelly. bellowing. No beer on the tundra. But...mammoth fights, cute baby mammoths...?
At first I thought, Ancient Egypt...naturally: witness the mighty construction site, walk the streets and look at the people. Mammoths, just furry elephants...meh. And I hate the cold.
But upon further consideration: even interesting, ancient people...are still people. I see 'interesting' people every day. So, for myself...I'm picking the mammoths: provided I can go on a warm Spring day and pack a lunch.