I constantly here people say " Only invest what you can afford to lose" Well no matter where your wealth is it could crash.
-Invest in USD- USA could collapse and experience mass inflation making your dollars nearly worthless
-Invest in Bonds- Government could collapse making your bonds worthless
-Invest in real estate- Housing prices could crash, natural disaster could hit and insurance company could go bankrupt
-Invest in metals- prices could crash, asteroid mining could collapse prices
Your money is never 100% safe no matter where it is invested.
Nothing is 100% safe, but there are things that are considered as investment, and these ones has high level of risk involved. The only thing there is never to rely on just one but diversify and keep your money in different assets/stocks, banks etc. Why Im saying this is so that when one fails, you will still have the others to rely on and wait for that one to recover. So nothing is safe.