The Sea Inside
Friedrich's greatest accomplishment was his ability to turn landscapes into a medium of physiological and spiritual biography. Here, he includes his own portrait within his landscape as a lay figure seen from behind -- a device intended to invite the viewer to look at the world through the lens of the artist's own personal perception. It would not be an exaggeration to take this picture as the essence of the Romantic approach to art.
Here, Friedrich has adapted the generic conventions of landscape painting to the demands of creative self-expression. Unwilling to have the artist serve as a mere "photographer" as it were of nature, Friedrich always took as his task the private and personal encounter of an individual with nature. Indeed, Friedrich was captivated by the idea of encountering nature in solitude in deepest revines, on the edge of the sea, or as here on the pinncacle of a mountain, which was about as far away from urban civilization as a European man could get. Indeed in his later paintings, Friedrich will continue to stress that the very idea of "self-expression" had to be associated with physical and spiritual isolation.
The Romantics believed that any artist who wanted to explore his own emotions, had necessarily to stand outside of the throng of money-making, political gimmickry, and urban noise in order to assert and maintain their positions.
*Taken from here.