AMSTERDAM - Dutch Crown Prince Willem-Alexander becomes Europe's youngest monarch on Tuesday when his mother, Queen Beatrix, abdicates and his country hails the avowedly 21st-century king with a massive, orange-hued party.
Willem-Alexander, 46, will be the first Dutch king since 1890 and the first of a new wave of European monarchs, with the average age of the current cohort at 71.
Amsterdam's population is set to double with at least 800,000 visitors flooding the city's streets and canals as Beatrix, 75, ends her 33-year reign by signing the act of abdication at the royal palace.
While Beatrix was known for her formal court, Willem-Alexander has already said that he and his glamourous Argentine-born queen consort Maxima, 41, will not be "protocol fetishists".
The king will be sworn in rather than crowned at deconsecrated church Nieuwe Kerk, a stone's throw from the palace, before a joint session of the houses of parliament.
The investiture will be attended by a number of other royals-in-waiting -- protocol dictates that reigning sovereigns are not invited, and will include Britain's Prince Charles, Spain's Prince Felipe and Japan's Prince Naruhito and his wife, Crown Princess Masako, who is on her first trip abroad in nearly seven years.
Beatrix's enthronement in 1980 was marred by violent protests and running street battles over a housing crisis that left the city looking like a war zone.
Anti-royalists this time have been allotted six locations in Amsterdam to stage protests. But only one has been booked by Republicans planning playful protests, including by wearing white.
Preparations for the day have been overshadowed by a rancorous debate about the event's official song, known as the Koningslied.
An online petition rejecting the song, an unusual mix of traditional and rap music, garnered 40,000 signatures within a few days.
Composer John Ewbank withdrew the song but the enthronement organising committee stuck with it.
The nation will now sing the Koningslied as one on Tuesday evening, just before the royal family heads off on a water pageant behind Amsterdam's central train station.
A cornucopia of concerts and club nights has been organised around the city, including an open-air set by world-famous Dutch DJ Armin van Buuren, and orange-themed street parties are planned across the nation.
The day will also be tinged with sadness for Maxima, whose father, Jorge Zorreguieta, and mother will be notable by their absence.
Zorreguieta, 85, a minister under the notorious Argentine regime of general Jorge Videla in the 1970s, also had to miss his daughter's 2002 marriage because of doubts over his role in the murderous junta.
Maxima is largely responsible for having made her husband popular after an allegedly boozy youth which earned him the nickname "Prince Pils".
Ever smiling, she has mastered the Dutch language and even taken a charity swim in Amsterdam's canals, endearing herself further in a country that expects their royals to be at once normal and regal.
Willem-Alexander's brother Friso will also be missed, in a coma following a skiing accident in Austria in February 2012.
Speaking ahead of the enthronement, Willem-Alexander said that "People can address me as they wish because then they can feel comfortable."
He stressed he wanted to "be a king that can bring society together, representative and encouraging in the 21st century".