That’s the 3-story Media Stand where the TV cameras for an inaugural parade are located...the first and fourth pictures at link will give you the perspective [click right arrow on photos]
https://www.mckinc.com/project/2017-presidential-inaugural-stands
“The Presidential Stands are constructed in front of the White House at 1600 Pennsylvania Avenue, NW to accommodate the President-Elect, his staff and family. The three-story Media Stand is located across Pennsylvania Avenue in Lafayette Park.”
I read the parade was cancelled a while ago. Thanks for link.
Just saw your post. thanks.