A global large cap etf is probably the closest thing to 'safe' over a 10+ year period - but there are no guarantees.
I invest in LGGG which is a fund that holds the world's largest 1500+ companies. If you buy one share in LGGG, you are buying tiny holdings in every large multinational that you can name - Boeing, Apple, Google, Shell, Exon Mobile, Toyota, Volkswagen, Samsung, Sony, Barclays, Chase, Astra Zenica, Pfizer, etc.
To lose everything, every single multinational would need to simultaneously go bankrupt. If that did happen, we'd be looking at a Mad Max style scenario, so it's not something I'd worry too much about.
Investments can still go up and down of course, but that fund is spread over all major economies, which helps to smooth things out - America, Japan, Germany, France, UK, Taiwan, South Korea, Canada, Italy, India, China, etc.