Travel is a major theme of many of his works and often shows the joy, isolation, and hope, all intermingling during the journey. Since Hopper was deeply interested in subjects that are commonplace, his focus is on the journey rather than the destination.
Hopper visited many places during his life time and managed to depict all of them in his art. His trips to Europe, New England, the American South, and Mexico were major inspiration for his travel-themed works. These paintings often depicted hotel rooms, trains, train station, bridges, roads, etc.
Approaching a City is a classic travel themed painting. In this, Hopper shows a railway track with a tunnel coming up. There are all kinds of buildings beyond the railroad track.
The view is not from the train, nor from the city, and the viewer feels as if they are looking in from the outside. The scene gives off a melancholy feeling, which is achieved by the dullness of the colours as well as the complete lack of any kind of nature.
Only a speck of the sky is visible in the background. It also lacks any kind of life, human or otherwise. The human-made structures are not inviting or exciting or beautiful and showcase the humdrum flow of city life.
As Hopper himself claimed, his aim was 'to depict the sad desolation of our suburban landscape'. The railroad lacks distinction and could be any place in any American city.
The railroad makes it easier for people to move around but this also means that there is less and less distinctiveness between these different places.
The painting now hangs in the Phillips Collection in Washington D.C., USA.