There is not such thing.
Every single thing can lose its value. In addition:
Real estate can be bombed in a war or confiscated[0] and is not mobile for obvious reasons[1].
Gold can be stolen, confiscated - and it happened already more than once.
Companies can go bankrupt.
Items - either productive like machinery or various stores of value like art are not immune.
Cash/bank accounts - well, money printing will get you here.
Cryptocurrency - ridiculously volatile, many exciting dangers, can be stolen remotely with no recourse.
You are looking for an unicorn.
[0] For "real estate will never go down in value" fans: https://en.wikipedia.org/wiki/File:Destroyed_Warsaw,_capital... https://en.wikipedia.org/wiki/File:German_Brennkommando-firi...
[1] Fun fact: Polish words for real estate is "nieruchomości", "nonmovables"
Every single thing can lose its value. In addition:
Real estate can be bombed in a war or confiscated[0] and is not mobile for obvious reasons[1].
Gold can be stolen, confiscated - and it happened already more than once.
Companies can go bankrupt.
Items - either productive like machinery or various stores of value like art are not immune.
Cash/bank accounts - well, money printing will get you here.
Cryptocurrency - ridiculously volatile, many exciting dangers, can be stolen remotely with no recourse.
You are looking for an unicorn.
[0] For "real estate will never go down in value" fans: https://en.wikipedia.org/wiki/File:Destroyed_Warsaw,_capital... https://en.wikipedia.org/wiki/File:German_Brennkommando-firi...
[1] Fun fact: Polish words for real estate is "nieruchomości", "nonmovables"