Which lines in the poem tell you what the surroundings of the house were like?

By "surroundings" I believe that the question is specifically asking for things that are not inside the house.  

Readers know that the poem is set during the evening or night.  We know this because line 2 tells readers that the front door is lit by moonlight.  Readers are also told that the house is alone.  It is not in a town, village, or neighborhood.  That detail can be found in line 14.  

The house is located in or near a forest because readers are told that the horse is eating grass from the forest floor.  Lines 3 and 4 are the following:

And his horse in the silence champed the grasses   

   Of the forest’s ferny floor: 

I believe that the forest is a fairly mature forest as well.  I believe this because line 24 tells readers that the sky is "starred and leafy."  This tells me that when a person looks up, they are looking at a tall forest canopy.  

The house is also located near a stone road.  If it is not a stone road, then I believe the house must have some kind of stone walkway leading up to it.  As the traveler leaves the house, the poem tells readers that the listeners hear the sound of "iron on stone."  That line is the third line from the end of the poem.  The iron that is on the stone is the horse's shoes hitting the walkway.