The a canopy-like structure that marks the tomb of st. peter and the high altar. both of which are located in st. peter's

Peter's Baldachin.

Explanation:

Peter's Baldachin is a sculptured bronze canopy called a Ciborium or Baladachin, it has a shape which looks like a cross and the center is stationed over the St Peter's tomb, this is also the location of St Peter's high altar in the Vatican city of Rome at the center of the crossing under the dome.

It was designed by Gian Lorenzo a sculptor and an architect.

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