The lectern is a great focal point in the square it is flanked on both sides by the Waterfall fountain, It is also a great vantage point from which to see the square.
It was designed as a speakers platform for the square to stand on and address the people below on the square, I have never seen it used for this though. The mosaic in the floor is a layout for the square below.
The entrance for the visitors center is below the lectern. read more