Across Europe, monarchies became casualties of World War I, swept away as a new political order was fashioned from the Continent's killing fields.
Today, the Spanish monarchy is perhaps the most politically significant in Europe.
King Juan Carlos earned the respect of Spaniards not only for his role in leading the democratic transition of his country after the death of dictator Francisco Franco in 1975, but also for defending the newly gained liberty during a failed coup in 1981.
Indeed, Juan Carlos is a sort of guarantor of democracy and liberty for Spaniards, says Carmen Enríquez, a journalist who has chronicled the Spanish royal family for more than 15 years.
"If the king had wanted, that coup would have been successful," Ms. Enríquez says. "If he hadn't come out on TV to oppose it, the military would not have stepped down."
Spain's popular king is the official head of state, but never intervenes publicly in politics. (Although at a 2007 Ibero-American summit he famously responded to leftist Venezuelan President Hugo Chávez, who was interrupting a Spanish official's speech, by asking "Why don't you shut up?")