Since its opening in 1971, Walt Disney World, in Lake Buena Vista, Fla., has undergone hundreds of changes as the popular family resort has grown exponentially, both adjusting to the demands of its tens of thousands of annual visitors, and adapting to different eras of entertainment and technology. Restaurants, live shows, and other rides are constantly in flux, and while many of these attractions are a distant memory, other discontinued attractions remain a welcome grip on a nostalgic visit to the Disney theme parks. Take a trip down memory lane by revisiting some of these long-lost attractions, including some favorites submitted by Boston.com readers.