The Forest that surrounds Castle Holdfast
The general rule is that people don't ride alone in the woods, except for exceptional reasons.
There are some characters who it won't apply to - notably Catriona. For the rest - even fairly tough characters like Ser Corryn Manderly, Hex and Nikomedes Sakellaris would hesitate before heading into the woods alone, and would prefer to take a companion. This applies to roads through the forest, as well as in the heart of the forest.
There may be an exception - the weirwood. There would be a gfamiliar track here and believers might take it to visit the old gods. I don't think any humans would attack them on such a pious mission.
Other things might, of course.
The Hardy children will know the woods immediately adjacent to the castle and have favoured routes, but they would be expected to travel together, or with a guard. Ser Kenrith Hardy will find many of the routes changed when he returns - he'll need to reaquaint himself with the woods.
Riding and travelling alone is pretty much discouraged wherever you are. The marshes are dangerous, like the woods. The meadows around Clearwater are safer, and the farmlands, but it would generally not be advisable to travel any distance alone.