For over three hundred years, people have tried to identify ideal landscapes in terms of paintings.
A landscape would be called picturesque if it resembled a painting by Claude Lorrain (1600-1682) or Nicolas Poussin. A tourist would travel with a darkened mirror called a 'Claude glass' or 'Lorrain mirror' to see a reflection that reminded them of a familiar landscape painting.
Scholars have debated what aesthetic factors qualify a scene as picturesque, and it usually boils down to a scene that satisfies the human instinct for beauty and the sublime. Others have said that there needs to be an element of roughness or variation, or a pleasing distribution of masses of trees or ruins.
The notion of what is picturesque has evolved as our taste for images has changed. If you google the term 'picturesque' all by itself, you don't get paintings; you get a lot of HDR photos of nature scenes with mountains and water features, and occasionally a domestic human structure integrated into the landscape. Our collective visual imagination is probably influenced as much by calendar photos and computer screen savers as it is by gallery paintings.
What do you think of when you hear the word "picturesque?"
Previously on GurneyJourney: Lorrain mirror
Picturesque in Wikipedia