Faux cast iron looks exactly like the real thing except that it is lightweight at about a tenth of the usual mass. This makes it easier to use in certain applications wherein a decorative element is needed by a support for heavy load cannot be supplied. It is also popular in outdoor applications where it can add drama without being problematic with corrosion or installation.
You will often find these on windows as ornamental treatments. They might cover the main window or the arch above. They may also improve the aesthetics of bare walls, ceiling fans, and door overhangs. For gardens, this element could be placed around flower beds for dramatic contrast between the metal and the colorful plants.
The results can be stunning. Check out examples online and see whether you might recreate some of them for your home.