(Courtesy .Fabio/Flickr)

On Thursday April 30, you'll find a party in Amsterdam that rivals New York City's New Year's celebrations. About 2 million people will flock to the Netherlands this year—dressed in bright orange—to take celebrate late Queen Juliana's birthday.

DJs jam out in public squares, music is blasted from boats in the canals, and streets devolve into one big vrijmarkt ("free market") where people barter off their old junk and clothes. It's the only day of each year when this enormous outdoor garage sale is legal.

Families typically go to 120-acre Vondelpark, where young children also set up small business stalls of their own—like lemonade stands, puppet theaters, and used toy sales. Kids can also take part in activities like face painting and theatrical performances.

But that only begins at 6 in the morning on Queen's Day. The partying actually starts at midnight the night before. Big name DJs hold outdoor parties in places like Stoperaplein or Museumplein, and beer flows freely on boat parties as well as in the streets.

Some advice if you're attending: Pace yourself the night before, because you'll have a long day waiting for you.

—Isha Dandavate for Budget Travel