When I was a boy, growing up in rural Illinois, it was common for gardeners to dig up some plants and store them in the basement for the winter.
I remember digging up gladiolas, cannas, dahlias, and some other tender perennials. It was like a harvest. I marveled at how big the corms, rhizomes, and tubers became. Some folks also dug up geraniums (pelargoniums) and save them by shaking off the soil, and hanging the upside down, inside paper grocery bags, in their basements. We also dug up sweet potatoes to eat, but also to save starts for next year. Ditto with potatoes.
The climate where I live now is milder, but freezing does occur each winter. Gladiolas survive the winter here. Dahlias sometimes do, but survival is less than 50%.
In my neighborhood, one gardener saves her geraniums each year. I haven't asked the method. Each year she digs them, and replants then next spring. They are nice sized shrubs, not just little bedding plants.
I have about a dozen large containers that I bring in. I keep them in the garage, unheated but dry and frost free. That's the brugmansias / angel's trumpets; zantadeschias / calla lilies; geraniums - I keep them in their containers and let them dry out; a couple of cacti. I also have some citrus that I keep in a cool sunny room.
There are also plants that I over-summer outside, but are really meant for indoor enjoyment. Those are smaller - Schlumbergera / Xmas cactus - starting to bloom now, and a bunch of orchids. I don't consider that overwintering because I have them to enjoy during the winter.
I wonder if over-wintering is becoming a lost art. With so much available at garden centers, maybe it isn't needed. I'm too cheap to buy them new each year. And I like the idea of shrub-sized pelargoniums, and lemons and kumquats from my own plants. Plus the citrus flowers have a very sweet fragrance, nice even if fruit doesn't form.
If I have the energy, maybe I should dig up some dahlias. I also have some potatoes that are already sprouting. I don't know of those will make it to Spring.
This link is for overwintering dahlias, gladiolias, cannas and pelargoniums. They discuss the hanging-upside-down method for pelargoniums. I don't know why they benefit from being upside down.
Thanks for the link; I bookmarked it. I used to save all those tubers in my basement or garage, but not this year. They rot in the ground as we speak. I used to get washing machine tubs and seal up the holes with wax and sawdust where I stored some of the tubers in sand. I gave that up several years ago when I had my heart surgery.