Depends what you mean by "safe".
Gold is considered a commodity investment, and shares the high volatility that is common in this class. (https://view.ingwb.com/sector-and-volatility-commodities)
Gold does have unique historic status as a currency or a backer of currency. I'm not in 100% agreement, but this does mean some see gold as a hedge against large-scale financial trouble.
However, that same historic status has made this asset in particular vulnerable to investment scams. (https://www.aarp.org/money/scams-fraud/info-2016/gold-coin-i...) This is one caution about this investment that you don't have to worry about as much compared to if you invest in, say, pork futures.
I would argue the "safest investment" is a diversified portfolio, personally.
