Oh wow! I find the colonnades of St. Peter's Square fascinating as well. As you know, these gigantic stone pillars were constructed at a time (1656 to 1667) when reinforced concrete (invented in 1849) was not yet available as construction technology. So, these massive Doric-styled columns are made entirely of stone and carry the overall loads of the upper roofing structures. Aside from the visual statement of presenting a glorious atmosphere for the public experience of nostalgia, these special building components also act as load-bearing members. Thus, the several rows of columns were technically designed by Gian Lorenzo Bernini for that specific purpose.
Thank you so much for your valuable insights and positive feedback. Stay awesome my friend. 😊
How interesting what you comment @storiesoferne, I did not dare to say it in the post because I was not sure, but while I was writing it I remembered that my impression of many elements of the square, including the columns, was that they were carved in travertine marble. Of course, maybe it's another stone with a similar beta, but that was my initial impression.
No worries. We can always research them online by asking Google haha. 😁 And you're right about the travertine marble. See, it's quite amazing how architecture can transport us to different times and places. I'm glad you have a keen interest in this field.