Japan's Crown Prince Naruhito began an eight-day trip to Spain on Wednesday (16.07.08). The prince is travelling without his wife, Crown Princess Masako, who is suffering from a stress-induced ailment, the Imperial Household Agency said. Naruhito visited Madrid's Prado Museum yesterday (17.07.08) and was also given the keys to the city, before attending a dinner hosted by Spain's King Juan Carlos. Today (18.07.08) he will make separate visits to Prime Minister Jose Luis Rodriguez Zapatero and Crown Prince Felipe, before leaving Madrid for Zaragoza tomorrow (19.07.08). Masako has been unable to accompany her husband on visits for several years due to the illness, which has kept her from most of her official duties. Masako, 44, has rarely emerged from the palace since she became unwell. Her last official trip abroad was in December 2002, when the royal couple visited Australia and New Zealand. The pressure of palace traditions and producing a male heir are believed to be factors in her illness. Naruhito said his wife was trying to overcome her ailment and appealed for public understanding last week.