Handling a birthday or holiday while away alone

I'll be away alone on my birthday. I'm not upset about it, but I don't want the day to dissolve into ordinary sightseeing and an early dinner. My current idea is one memorable activity, a nice meal and a call home, without making the whole thing feel like a compulsory celebration. Have you spent a holiday or birthday solo while traveling? What made it feel meaningful rather than just another date in the itinerary?