No, it is not, and for a few reasons. First of all, a rotunda is not a spere, it is a structure with a circular base and usually has a domed roof. It is not actually a sphere. Also, the earth was created by a gravity which, over time, collected debris and rocks from nearby space, and was not man-made. A rotunda is man-made, and is usually made of cement and/or brick. There fore the earth is NOT a rotunda. I hope I helped