Water Park of America
With 10-storey water slides, long lazy river, and much more, this water park is attached to the Radisson Hotel Bloomington, around the corner from the Mall of America in Bloomington (near Minneapolis.)
Best Western Edgewater Resort & Waterpark
In Duluth on the north shore of Lake Superior, The Edgewater has complimentary breakfast, playground, bicycles, mini-golf; and, opening in 2006, a 30,000 sq. ft. indoor waterpark, with Polynesian theme, lazy river, 40-storey slides, vortex pool, play area for younger kids, and exploding "volcano".
The Arrowhead Lodge at Brainerd Lakes
30,000 sq. ft. Paul Bunyan indoor waterpark has 500 feet of waterslides -- including a "holographic tube slide" with lights and sound-- and a treehouse activity center.
Arrowhead Resort: Big Splash Waterpark
On Lake Darling-- 130 miles NW of the Twin Cities-- Arrowhead Resort's 38,000 sq. ft. waterpark has 4-story slides, lazy river, children's play fort with water blasters, geysers and 500 gallon splash bucket.
Rapid River Lodge and Waterpark
In Baxter, this Lodge has a modest-sized 13,000 sq. ft waterpark, with tube slide, lazy river with waterfall and rapids, kiddie pool with skides and water features.
More MN Resorts with Water Parks
Every year sees more resorts with indoor water parks. About.com's Guide for Theme Parks is keeping track!