A popular rum-based cocktail in the Bahamas. Nassau Royal liqueur is made in the Bahamas and was originally sold as a tourist souvenir. But it became so popularity that it soon was available in other regions. It can also be purchased online. It's a citrus-based liqueur with undertones of coffee, vanilla and other island spices. If you can't find it anywhere, you can substitute Orange Curacao which is the closest in overall flavor. It won't impart the exact same flavor to the cocktail, but only a minimal amount is needed (to provide a fleeting hint of citrus).