Heilige Hallen, Protected beech forest reserve in Feldberger Seenlandschaft, Germany.

Heilige Hallen is a protected old beech wood in the Feldberger Seenlandschaft, 3.5 kilometres west of Feldberg. The nature reserve covers 65.5 hectares, of which 39.2 hectares have been left unmanaged since 1998. Some beeches reach 53 metres in height and up to 350 years in age, and several have passed their natural lifespan, so dead wood is left standing and lying. The wood also holds several Sölle, hollows with ponds, kettle bogs and birch carr.

In the mid-19th century, Grand Duke George of Strelitz, impressed by the giant columnar beeches, ordered the woodland to be spared for all time. Its 25-hectare core was listed as a natural monument in 1908 and became a nature reserve on 24 February 1938. The protected area was enlarged to 65.5 hectares in 1993.

The name Heilige Hallen, meaning Sacred Halls, comes from how the tall beech trunks rising toward a closed canopy call to mind the interior of a church. Visitors walking through the rows of trees can feel why this comparison has endured for so long.

The reserve is accessible via marked trails, and the nearby Waldmuseum Lüttenhagen serves as a starting point with information about the forest and guided tours. The paths are mostly flat and straightforward to follow for most visitors.

Since 1950, fallen and dead trees have been left where they lie, so the forest floor is now layered with slowly decomposing wood. This makes the reserve a habitat for rare beetles, fungi, and woodpeckers that rely on deadwood in ways that few other forests nearby can offer.