Theory:

     One of the pictures was of a swing hanging from a branch half-hidden in dense foliage, and in the checkered light and shade of this bower, two persons were swinging; and there was another of a broad flight of steps leading into some castle-like palace, up and down which men and women in festive garb were going and coming. When the light fell on the windows, these pictures shone wonderfully, seeming to fill the river-side atmosphere with holiday music. Some far-away long-forgotten revelry seemed to be expressing itself in silent words of light; the love thrills of the swinging couple making alive with their eternal story the woodlands of the river bank.
 
     The topmost room of the house was in a round tower with windows opening to every side. This I used as my room for writing poetry. Nothing could be seen from thence save the tops of the surrounding trees, and the open sky. I was then busy with the Evening Songs and of this room I wrote:
 
     There, where in the breast of limitless space clouds are laid to sleep,
 
     I have built my house for thee, O Poesy!
Explanation:
 
Out of the colourful pictures, one picture was of a swing hanging from a tree branch, hidden inside the thick leaves of the trees. In the pleasant shade of the tree, two persons were playing in the swing, and multicoloured lights reflected on them.
 
Swing photo.jpg
One of the pictures was of a swing with two persons glowing in the checkered light!
 
There was another broad series of steps that led to the palace, which looked like a castle. Many people were moving about in fancy clothes. When sunlight fell on the stained glass windows, the pictures shone beautifully, which seemed to fill the place with pleasant music. There seemed to be a festive atmosphere of a long-awaited celebration, and all expressed through the light. The author's imagination is at his best when it comes to describing the atmosphere of the place. The swinging couple on the picture and their love story all seemed to come alive, in the banks of river-side.
 
The topmost room of the house was in a round tower which had windows on all sides. This was the room used by the author for writing poetry. He could not see anything from there except the top parts of trees and the sky. He was busy with writing Evening Songs, and he also wrote a poem about the room:
 
"There, where in the breast of limitless space clouds are laid to sleep, I have built my house for thee, O Poesy!"
 
He says in the lines that he had built his house in the midst of a huge space without any boundaries, where even clouds stop to sleep - only for the sake of poetry.
 
Meanings of difficult words:
  
No.
Words
Meanings
1
foliageplant leaves collectively
2
checkereddivided into an arrangement of squares of different colour
3
bowera pleasant shady place under trees
4
garbclothing, especially of a distinctive or special kind
5
revelrylively and noisy festivities
6
thencefrom a place or source previously mentioned
7
Poesypoetry
8
Theeold-fashioned term for "you"
Reference:
State Council of Educational Research and Training (2019). Term-2 English Standard-8. My Reminiscence - Rabindranath Tagore(pp. 113-126). Published by the Tamil Nadu Textbook and Educational Services Corporation