Everyone should be familiar with this world. It's the one that always appeared on Minecraft's main-menu (title-screen), blurred and slowly rotating.
It first appeared in 2011 for Minecraft Beta 1.8 and remained for many years, it was only recently replaced in 1.13 each subsequent version.



The seed was found on 18th of July 2020 at around 5:45 AM UTC.

Version: Beta 1.7.3
Coordinates: X=61.48~, Y=75, Z=-68.73~
Seed: 2151901553968352745 OR 8091867987493326313 (both work)



Why two seeds? There are actually 2^16 (=65536) seeds that will all generate the same world. Older versions of Minecraft used only 48 of the bits of the seed. Here's the formula for getting all of them, as explained by Earthcomputer:
25357015387625 + 2^48k, 0 <= k < 2^16; (k is an integer)
The two seeds mentioned are the only "valid" seeds, in the sense that they can be naturally generated by Minecraft (due to Java's random function implementation).
There is not any word/string of characters that will produce this seed, it was generated randomly.
This has nothing to do with "shadow seeds", they are not present in these versions.
What can change is placement of trees and fauna as that depends on the order chunks are generated; otherwise, there are no differences between the two seeds.

Earthcomputer, Cortex, Neil - wrote the biome and terrain checking code
DutChen18 - made multiple tools/mods to help with the recreation and gathering data for the seed checking
MC PseudoGravity - reversed the tallgrass colors and found the biome values in the panorama
Philipp_DE - hosted the recreation server and screenshot bot
Tomlacko - started the project, found the coordinates, produced the panorama viewer with recreation overlay
...many other people helped in other ways (such as building the recreation block-by-block) listed here.

To see how this was accomplished, watch SalC1's video: https://www.youtube.com/watch?v=GaRurhiK-Lk

Seed reveal video from Earthcomputer: https://www.youtube.com/watch?v=caLCZNLPgrM

~ this post copied mostly in verbatim from Tomlacko's Reddit post on the subject

Why post about this so late? In fact, why not post about seed.png or the Skull on Fire Painting?
(I know the painting wasn't found through M@H, but still. It's much more recent than the panorama...)

Could we quit posting enormous pictures that get downloaded to our machines? The GPU has trouble viewing them.