Not a zoo, despite the name — the Tiergarten is a 112-hectare recreational forest in the Kirchrode district where roughly 120 fallow deer roam free, much as they have since Duke Johann Friedrich set the first herd loose here in 1679. You walk in for free, follow paths through old-growth oaks and beeches, and the deer are genuinely everywhere — grazing in clearings, crossing your path, entirely unbothered. A separate Hubertus enclosure holds red deer, and birders come for the woodpeckers and rare bat species.
The annual Tiergartenfest is a charming local tradition: children collect acorns and chestnuts to feed the animals over winter, and the festival is held to thank them for it.