Trouble trying to add this basemap to ArcGIS online MapViewer

[GregG]

I am trying to add this as a basemap to the MapViewer as a basemap. I tried inserting the link into the add from web URL and nothing happens. Any help would be appreciated. Test it out and see if you can figure it out. Thanks

Here is the URL  https://maps.c-map.com/cmap_embed.htm?

[ReeseFacendini]

In order to add a custom basemap to your web map, it needs to be available as a REST, WMS OGC, or WMTS OGC layer.  There isn't a way to take the URL above and extract the data source URL from it.