Holy Stairs or Scala Santa is right across the street from the Cathedral of St. John Lateran. The best way to get there is with the Metro A - San Giovanni stop or with the Hop on hop off bus Roma Cristiana.
According to the Catholic tradition, Christ walked up these steps as he was condemned to death by crucifixion. These steps were brought from Jerusalem to Rome in the 4th century by St Helena, the mother of emperor Constantine and placed in this church.
Tradition dictates that you must ascend the Holy Stairs on your knees. There are 28 of them. They’re covered in wood, with cut outs on the risers where you may touch the stairs. There are some small areas covered in glass with the bloodstains of Christ.
I loved the experience of climbing the steps on my knees. To climb the steps as Jesus did is an emotional and humbling experience. Your knees begin to hurt, but just think of the pain that Jesus went through carrying a cross and bearing the pain of being beaten. Then you can manage the few moments of pain from crawling up the steps I would definitely recommend making the climb. When you reach the top of the Holy Stairs you can visit Sancta Sanctorum (Holy of Holies). It was the personal chapel of the early Popes. There are some beautiful frescoes. What I loved the most was the display in a glass case. It housed the fragment of the table on which the Last Supper was served.
I feel this is the ultimate must do if you visit Rome. It's so inspiring and you get a great feeling of accomplishment afterwards. It was worth it to me. I went early morning and it was almost empty.