
From Wikipedia: In recent years, Koninginnedag (Queen's Day) has become more and more of an open-air party, with many concerts and special events in public spaces, particularly in Amsterdam, which attracts anywhere from 500,000 to 800,000 visitors. Many Dutch people living abroad try to make the pilgrimage home (with many 'clued-up' tourists) to experience this holiday each year. Booking accommodations in Amsterdam and elsewhere for Queen's Day is notoriously difficult, requiring booking 6 months or more ahead.

Woo! And we just happened upon it.
In 2005, we decided to relive Queen's Day here at home so we had a party:

And then this past Saturday we had our 3rd Queen's Day (Second in the US):
It was a delightful event full of beer, hot dogs and ultimate family matching.
Awesome.