One of my very favorite moments in history for art and architecture is the Art Nouveau period - roughly 1890-1910. It was most popular in Europe and can still be seen all over France, Austria, Spain and elsewhere. My understanding is that it was a "back to nature" movement, where artists were interested in harmonizing their environments with the natural world around them. (Obviously, I'm not an art historian...) Mostly I'm drawn to the undulating lines, circular motifs and highly ornate decorative details. Here are some beautiful examples of doors crafted in the Art Nouveau style.