The site of protein synthesis is called a ribosome. Ribosomes are found in two locations:

* Cytoplasm: Free ribosomes float freely in the cytoplasm and synthesize proteins that will be used within the cell itself.

* Rough ER: Ribosomes bound to the endoplasmic reticulum (ER) are called bound ribosomes. These ribosomes synthesize proteins that will be exported out of the cell or inserted into membranes.

So, the answer to your question is ribosomes.