On a whim a few years ago I attended Knuth80[0], a symposium celebrating Knuth's 80th birthday in Piteå, northern Sweden. I traveled there by train from London and spent a few days listening to fascinating lectures and attending the inaugural performance of Fantasia Apocalyptica, performed by Jan Overduin on the wonderful new pipe organ in Piteå. I only had the opportunity to speak briefly with Knuth, but the whole thing (including the location in northern Sweden in winter!) was a wonderful experience, and should there be any further birthday symposiums I would heartily recommend them to anyone!
[0] https://cs.stanford.edu/content/contacting-donald-knuth/news...