For two weeks every spring, the Royal Greenhouses open their doors and invite us commoners into a majestic feast for all of the senses. Locals never miss it, and if you happen to be in Brussels during this time, you must go. Most tourists visit during the day, but I highly recommend going around dusk (from 8-10pm), right before the gardens close. There are less people and the atmosphere is utterly magical. The flora takes on a new mysticism under a moonlit rotunda. Once you step through the art nouveau architecture, you feel like you're royalty from long ago. Admission is cheap (2.5euro) or even free if you're a student.