What is the main setting in the poem, On Turning Ten?

The poem takes place in and around the speaker’s childhood bedroom, where they are reflecting on their impending mortality. Little description is given apart from a bed and a window; the window looks down over their backyard, and they can see their treehouse and garage. There is an implication that this room once contained the speaker’s entire world, and now it is shrinking around them as the world outside gets bigger.