We have started to get drawings from Civil consultants in the 2018 file format. Thanks to our recent move to the AEC Collection, we now have access to AutoCAD® Civil 3D®. I have no idea how to use that program, beyond the AutoCAD basics, but I installed the 2018 version of it in the hope that I would be able to export the received drawing to "vanilla" AutoCAD®. Similar to AutoCAD® Architecture and AutoCAD® MEP, you can go to the Application Menu > Export > Export Civil 3D Drawing to export a drawing. There is a dialog, where you can choose between AutoCAD DWG and Microstation® DGN, and, for DWG export, the Export Settings allow you to select a file format, such as 2013.
I did all of that, and Civil 3D did its thing, and drawings were generated. (I got more than one because I left the Include sheets toggle checked, so a drawing for each layout was also generated.) I fired up AutoCAD Architecture 2016 and opened the exported "Model" file, only to be greeted by this dialog:
Still, I expected to have a "clean" 2013-format file that only has non-AEC AutoCAD objects. I tried a Window selection in Model Space to get all the visible objects and then tried to copy them to the clipboard, hoping that if I pasted them in a new file, the future AEC Objects would not come along for the ride. That did not work, as the copy to clipboard failed.
Finally, I tried starting a new drawing and using the INSERT command to insert the originally exported "Model" drawing file. I received the following dialog: