Bedrich Smetana's Die Moldau has been one of the most evocative pieces of music I have listened to. The piece exudes very clear imagery; a river, soothing at times, playful and dancing at others. To me, the piece also seems special, because I can perceive a genuine love and affection for the river that is structured in the notes.
Especially the opening pipes, and the middle change of note, is vivid and effective. The somewhat melancholy main theme played by oboes and first violins is exceptional, and has a sweeping continuity which I just love. The whole drama builds up to a grand fortissimo near the end.
However, I was not aware that you could actually construe a whole series of events taking place alongside the river, from the time it begins as two small streams, upto its meandering bend when it enters Prague.
This site gives a very succcint and engaging description of the events which the transitions in the piece signify; these include a group of hunters hunting, a peasant wedding celebration, and then the vast vista of Prague. As the site mentions, Smetana was a nationalist and drew inspiration from folk music and style, so it should not be suprising that the notes signify such folk celebrations and events.
Take a look.