Nan Desu Kan (NDK) is an annual three-day anime convention held during September at the Gaylord Rockies Resort & Convention Center in Aurora, Colorado. The convention is the largest anime convention in the Rocky Mountain region and each one takes eighteen months to plan. Its name in Japanese roughly means nan desu ka (何ですか), "what is it?". The parent company, Rocky Mountain Anime Association, is a registered 501(c)(4) nonprofit organization.