Where did you see them? There are many large begonias - Lotusland, Challenger, Paul Hernandez, nelumbiifolia, Caribbean King, Caribbean Queen, Maggie Nodal, heracleifolia, Selph's Mahogany, and many others.

Some very large ones I've only seen online are baccata and parviflora but would love to see them in person.

Sorry, I never got back to you. These were in Corinth, MS. at a motel. They looked like my angel wings, but were about 5 feet tall and that wide. They were beautiful. They were planted in the ground. I only have one kind, but I have never planted it in the ground but I am going to try it this spring.
Thanks,
Patsey

From what I understand some of the angelwing types ( cane stemmed) can get easily over ten feet tall and once I do believe I saw some container ones in a White House shot on one of the porches or steps that was huge., but they do get big

I thought you meant big as in big leaf, big bones instead of tall.

Some canes do get very tall. The tallest I saw was at a nursery in San Francisco this summer.

Here it is - B. luxurians
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B. maculata grown to near perfection at the convention in Miami 2006 about five feet tall.
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Irene Nuss grown by my mother (cuttings from me) is approaching six feet.
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This is either Lana or some other similar superba cane along with Maurice Amey at Discovery Cove in Orlando.
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A Sinbad I grew a few years ago in an 18 inch container along with Torch, Richmondensis, and Chocolate.
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Oh my gosh, I have never seen any like this down here. I am going to have to get some of these. I guess they need shade in this high heat. Thanks for the pictures.
I had one, took four cuttings, they bloomed a little outside but they did grow. I brought them inside for the winter and they have bloomed ever since.
Thanks again,
Patsey

Meems at Hoe & Shovel (just north of Tampa, FL) grows cane begonias that can get over 10' tall. See link to her blog, below. I linked it to her Angel Wing Cane Begonia page.

A cane begonia that is similar to Meem's can be purchased on Amazon:
http://www.amazon.com/gp/product/B002SWAQMA

Here is a link that might be useful: Hoe and Shovel - Angel Wing Cane Begonia

And here is a link to an enormous white cane begonia that I saw on the internet awhile back.

Here is a link that might be useful: Garden Amateur - White Begonia