The Huldrawood is a forest which is located just outside the urban area of Trolberg.
The forest is at least partly located within the city walls of Trolberg, since Camp Sparrow is located in the part within the walls. The various maps of Trolberg and surrounding area seen in the graphic novels and tie-in-books, as well as depictions of the Huldrawood itself in all 3 continuities, contradict each other on whether or not the Huldrawood is entirely within the city walls, or if it is also partly outside the wall.
The End-Of-Year camp of the Sparrow Scouts is held here. In the animated series and tie-in-books, the Huldrawood is also the home of the Marra, who gather here to share their stories of the nightmares they gave to people.
According to the map seen in the graphic novels, there is a hill in the center of the woods with a tower called The Witch's Tower. In the animated series and the tie-in novels however, this tower is eventually revealed to be located underneath the Library. This map also depicts several figures resembling Forest Giants in the forest, though other proof of this has yet to be seen.
Despite the aforementioned residents, the Huldrawood itself seems entirely mundane. It is a dark forest of tall pine trees, though they don't reach the height of the trees in The Great Forest.
In the animated series, a field with a few short trees and a dirt trail is separated from the Huldrawood by a decrepit gate and a crumbling, mossy stone wall.