Every lesson that Helen was taught by her teacher was set amidst the beauty and magnificence of nature. What are some examples of this from the text?

To find some examples, take a look at Chapter Seven.  Here Helen talks about the relationship between nature and her lessons, noting that Miss Sullivan preferred to teach her out of doors rather than in the house. For Miss Sullivan nature became as much a part of Helen's education as learning to read and write:

Indeed, everything that could hum, or buzz, or sing, or bloom, had a part in my education.

As part of her geography lessons, for example, Miss Sullivan encouraged Helen to make a dam from pebbles and to dig her own river beds and islands. She also used clay to make a map of the world with raised sections to indicate mountain ridges. Helen could thus trace her finger along these raised sections to learn about the geography of the world.
By setting Helen's lessons outside and by utilizing the natural world to teach, Miss Sullivan instilled in Helen a genuine love of learning and of life, more generally:

When she came, everything about me breathed of love and joy and was full of meaning. She has never since let pass an opportunity to point out the beauty that is in everything.

Helen Keller writes in The Story of My Life about how her teacher, Anne Sullivan, taught her in the outdoors. She writes in Chapter V:

"Long before I learned to do a sum in arithmetic or describe the shape of the earth, Miss Sullivan had taught me to find beauty in the fragrant woods, in every blade of grass."

Sullivan brings her student to nature to learn about the world around her and to teach her the names of objects in nature using sign language. 
Nature also helps Keller learn the meaning of abstract ideas. As she is trying to understand what love means, she observes the following in nature:

"The sun had been under a cloud all day, and there had been brief showers; but suddenly the sun broke forth in all its southern splendor."

The natural world allows her to understand more complex concepts such as love, as she equates the appearance of the warmth of the sun after a day of storms with the concept of love. By bringing Keller outside, Sullivan makes her lessons enjoyable. As Keller writes, "The loveliness of things taught me all their use." Keller's early enjoyment of her lessons outside causes her to be eager to learn more, setting her on a path that will take her to Radcliffe College (then the sister school of Harvard) and to a life of learning, speaking, and activism.