Walpurgis Night - the Eve of May Day

Now, finally, spring is here. And with Walpurgis night we could celebrate for real.
For me, it was an ideal day, with sunshine, a lot of outdoor time and my family around me. I couldn't ask for more.
How about you? How did you spend Walpurgis night? Did you see any bonfires, or did you, like me, make your own at home?
Do you know why we celebrate this day?