This archway was built as part of a full basement renovation that involved patching, painting, lighting upgrades, several repairs and a few other custom installations. A non-load bearing wall was broken through and re-framed to create the desired opening.  An approximate radius was built into the upper corners of the opening from 2×4 chunks and sheet stock.  Then sheetrock was applied to all surfaces of the wooden sub structure.  Corner beading was applied, plaster to perfection, then paint.