The landscape the poem takes us to is fairly non-specific, but we can imagine it clearly nonetheless. The speaker describes a train winding its way over miles, dipping through valleys and around and into mountains. The speaker commands a view of the train's whole course through this scenery, and sees it punctually pull into a station at the end of the line. Whenever we read this poem, we imagine ourselves standing where the speaker is – perhaps at the crest of a hill or mountain top, watching the train as it huffs and puffs its way through the countryside lying before us. To us 21st century, car-driving readers, it's a scenic, romantic view, and we like to linger there and "watch it lap the Miles."
If we're taking the biographical route with this poem, we might imagine the real-life landscape that Dickinson was writing about – the hills and valleys of her native Massachusetts, as the first railroad trains rolled in and out of her hometown, Amherst. The town, situated in verdant western Massachusetts, is close to the Holyoke mountains, and we can just imagine a steaming train winding through the trees and fields of a 19th-century landscape (for help with this imaginary exercise, think of those terrific aerial shots of the Hogwarts Express winding through the verdant English countryside in the Harry Potter films).