For me, serendipity is the greatest pleasure of sketching.
Turning a corner, I can be suddenly struck by what's before me. I think, "I want to draw that!" and I sit and start immediately. The composition and the light are so pleasing. I can fall in love simply with the forms of the drawing. Coming upon them is a delightful discovery - a pleasant surprise.
Other kinds of serendipity can happen too, involving the content of the drawing. At times it's a story of the drawing itself. Something interesting happens that I observe. After all, I'm a long sketcher. I draw for hours, not minutes and I witness quite a lot, while sitting there attentively. Or, a pleasant surprise happens in the ink on the page - a splash or a drip entertains rather than disappoints.
Other times, it's a story of the subject. I come to find out that what I've drawn has significance far beyond what I ever knew at the time. That's what happened with this drawing. I created it two years ago, in the central Italian town of Montefiascone. I remember it being a rough drawing day. I walked and walked and found nothing that tickled my fancy. Finally, I was stunned by this view, and plopped down to draw - chasing the shadows across the old building before me. As I drew, priests quietly passed behind me. On the wall was a old stone plaque that said "Typographia Seminarii". I "googled" the subject when I got home, but found no trace of the place. I figured that I had simply found a pretty place.
Just this week however, I learned that the building did have significance- and quite a story. Turns out, it's the location of important library started in the late 1600's that was brought to light in 1987 - filled with decaying, rare books. No one had cared much for the books for years, and leaking plumbing had put the treasures in peril. Long before, the library was harmed by Napoleon's invasion of Italy and by World War II (There's a machine gun bullet in one book!) Some of the books dated back to the 1400's, and all of them were collected by the important bishops who controlled this seminary which sits on the road to Rome. The library's fragile state spurred the creation of a well regarded summer school of book conservation. You can read about it here, and listen to a short, interesting British radio interview with experts on the library, here.
I guess you can never close the book on a sketch. There may be hidden chapters.