Stand beside one of eight surviving Big Boy locomotives
The largest steam engine ever built
A transport museum in Denver whose centrepiece is Union Pacific Big Boy 4005 — one of the largest steam locomotives ever built — displayed indoors alongside several hundred vehicles.
Why it's unique
Only twenty-five Big Boys were ever built and eight survive. This is one of very few kept under cover; most of the others sit outdoors slowly weathering in parks.
Being indoors is what makes it worth the trip. You can walk its full length in good light, at close range, without it being a hundred feet away behind a fence, and the scale of the thing at that distance is the entire experience. 4005 ran roughly a million miles before retirement.
Before you go
The locomotive is the reason to go but the rest of the collection is substantial — several hundred vehicles including some genuinely obscure early cars.
Allow two hours, and start with the Big Boy while you are still fresh.