The daughter of Queen Mary and King Frederik X of Denmark dazzled on Friday as she stepped out in a stunning baby blue suit at Aarhus City Hall in Denmark.

Princess Ariane turned 18 on Thursday. This means that all King Willem-Alexander and Queen Maxima’s daughters are now adults. Ariane will not be celebrating her birthday with her parents on Thursday. Queen Maxima had said previously that her daughter is very busy with her studies at United World College Adriatic in Italy. “We are very proud of her. But she will be very busy with her final exams during her birthday and afterward," the Queen said after the state visit to Kenya. “We already have an empty nest, so this is just a confirmation of that.”

Though Princess Isabella was the star of the show at her 18th birthday party at Aarhus City Hall, the young royal turned the love back onto the city “that has great meaning to me and...