Visiting a fern garden is one of the best ways to see the enormous diversity of ferns and their uses in the landscape. At the Morris Arboretum in Philadelphia, Pennsylvania, there is a restored fern conservatory originally built in 1899 by John Morris. This fernery contains many rare and exotic ferns in a sunken structure under glass. According to Shelley Dillard, a plant propagator who tends the ferns, the restored structure has ferns from slightly cooler zones but is the only true Victorian fernery in North America containing the prerequisite features such as a waterfall, a grotto, and a bridge.
Another restored 19th-century fernery is Ascog Hall Victorian Fernery and Gardens on the island of Bute, in Scotland. They have a huge rhizome of a king fern (Todea barbara) that, according to an article written at the time of the original fernery in the 1899 Gardener's Chronicle, may be 1,000 years old or more.
If you aren't going to be in Philly or Scotland any time soon, check out the Hardy Fern Foundation. It's an organization dedicated to educating the public about ferns. Their website has an extensive list of fern collections at botanical gardens and arboretums across the country. They also publish the Directory of Fern Gardens, Nurseries, and Reserves in the United States and Canada, which is available via mail order.