Like most sites, the very first webpage ever created, back in 1989, no longer exists. But one of its immediate successors does.
At the Hypertext 91 conference in San Antonio, creator Tim Berners-Lee took what he then called the "World Wide Web", set up a demo in the conference hall and showed people the future.
As Motherboard notes, Berners-Lee had physical copies of the Web there to give out. Because there was no internet porn yet, nor a fascination with cats, the whole thing fit on a floppy disk. Its contents were soon uploaded here, where they've been for over 20 years.
I don't know if you could even put a physical approximation on the size of the world wide web today. It's certainly bigger than a floppy disk. Or even a black box.
What It Was Like to Surf the Web in 1989 [Motherboard]