Using inches for modeling products and characters (furniture, creatures, weapons, etc.) Use feet for architecture (houses, skyscrapers, etc.) Use miles for environments (i.e. mountains, valleys, and landforms)
First apply spline in the top viewport. Then, apply lathe to create a 3-dimensional plane object. go into perspective viewport, and youll see those results. Optional: convert to editable poly and apply the shell modifier to create a 3d object with soft thickness.