1 Miniatur Wunderland

Where: Hamburg, Germany

You can't have a list of extreme model railways without mentioning Frederik and Gerrit Braun. The German twin brothers created the granddaddy of them all: Miniatur Wunderland.

The über model built in HO scale—which is the most popular scale of model railway in the world, and works out to 3.5mm to 1-foot—supports 39,000 feet of track, and requires 46 computers to coordinate an ever-growing network of signals and switches. Those lucky enough to make it through 6 miles of model railway heaven (this is more than a day trip) are treated to eight sections based on landmarks from around the world. At the scale models of the American Rockies and the Swiss Matterhorn, visitors can climb stairs to reach the summits (nearly 20 feet high) to view Wunderland from an elevated perspective. A simulated sunset highlights Las Vegas, where 30,000 lights replicate the glow of Sin City. Finally, don't forget to visit Knuffingen International Airport, modeled after Hamburg's own International Airport, the largest model airport of its kind. See planes cleared for simulated takeoffs and landings taxiing down the runway.

And the Brauns aren't done yet. New construction plans, including sections for Italy, Africa, and a potential futuristic landscape, reach into 2020. Wunderland's wow factor is nearly endless.