These are called “bog bodies” and they’re so alive-looking that they’re sometimes even called “bog people.” They’re found in the sphagnum bogs in Northern Europe and unlike most ancient human remains, they’ve retained their external and internal organs. The conditions that allow this to happen include highly acidic water, low temperatures, and a lack of oxygen. 

The bog bodies’ skin however, is severely tanned and their bones have lost much of their calcium phosphate. The German scientist Dr. Alfred Dieck discovered over 1,850 of these Bog Bodies in 1965 but many cannot be verified by documents or archeological finds. In fact, there’s an entire article in the German archeology journal claiming that some of the cases were false. 

Dieck thought that the bodies were of the first victims of human sacrifice in Iron Age Germanic paganism, while others think that “bogging” was a form of capital punishment in 1st century Germania. Either way it’s interesting, that in a sense, these people are immortalized after their deaths. 

(Source)