I spent about three days at the Edinburgh Fringe Festival in August, 2001. I had never been to (and haven't been to since) a performing arts festival, so I have no basis for comparison in that sense, but it was one of the most fun experiences I ever had. It was wall-to-wall plays, musicals, stand up performances and one-man shows.
I was in Edinburgh with a friend, but her plan was to see the sights during the day and see shows at night. The draw of the stage was too much for me, though. I didn't see a single castle or museum while in Edinburgh. I can't recall what all I saw, but I can remember some. Margaret Cho
The weather was gray, cool and occaisonally rainy, which somehow seems appropriate to a performing arts festival. The notion of stepping from cool, cloudy conditions across a threshhold into a theater warm with body heat, the stage as bright as the sky was not, is so perfect that I'm not sure I trust my memory.
Every August since 2001 I've wished I was in Edinburgh. Like I said, I don't have sufficient basis for comparison to say that the Fringe is really the top of the heap when it comes to performing arts festivals, but I'm not sure anything could ever compare to the first I ever attended.