This is assuming a world-wide disaster which may not happen. Land is currently overpriced (at least in the NorthEast) and real estate prices haven't come down that much. Maybe good for diversification like you said but I don't know if a large amount of $, percentage-wise should be parked there.
You can also buy collectible or high-value assets (used in good condition). For example, I own a very large high quality telescope with a 20 inch mirror, bought it used and in great condition (saved 40%). In 10 or 20 years, I should be able to sell it, and get an inflation-adjusted equivalent used price then, preserving my money and giving me an enjoyable hobby in the meantime.