American philanthropist Andrew Carnegie donated over a million dollars towards the construction of this immense mock-Gothic palace, home to the International Court of Justice and the Permanent Court of Arbitration. The building was designed by French architect Louis Cordonnier and completed in 1913; today it can be visited only by guided tour with reservations made online ahead of time. You’ll see most of the ornate apartments and marvel at the grandiose gifts given by each of the participating countries: crystal chandeliers made with real rubies and emeralds and each weighing 1,750kg (3,900 lb.) from Delft; incredible mosaic floors from France; a huge Turkish carpet woven in 1926 in Izmir; and an immense 3,500kg (7,700 lb.) vase from Czar Nicholas of Russia. If the courts aren’t in session, your guide will take you inside the International Court of Justice, which handles all of the UN’s judicial cases. Tours last 45 minutes.