Behind Den Gamle By is Aarhus’ fabulous Botanical Garden (sciencemuseene.dk; free), a green retreat of rockeries, rose gardens, hothouses and picnic spots. It's part of the Aarhus Science Museum. The dome-shaped walk-through glasshouses have Mediterranean, desert, forest and tropical habitats. The tropical house with its spiraling wooden staircase is at its center, and it doubles as a fluttering butterfly house.