For the blacksmithing tool:
* Forge: This is a broader term that refers to the entire workspace, including the anvil, but can also be used to refer specifically to the anvil itself.
* Stithy: A slightly archaic word for an anvil.
* Hearth: This refers to the area where the blacksmith works, which includes the anvil.
For the general concept of a solid, unyielding surface:
* Base: This is a very general term, but can work in some contexts.
* Foundation: This emphasizes the solid, stable aspect of an anvil.
* Platform: This emphasizes the flat surface of an anvil.
The best synonym for "anvil" depends on the specific context and the desired level of formality.