Rings of PowerRings of Power - This is the region (Eregion) where the Rings (save the One Ring itself) were forged during the Second Age.  The Elf, Celebrimbor, worked with Sauron (who was disguised as Annatar); however, Celebrimbor forged the Three Elven Rings without Sauron's knowledge, and Sauron, likewise, forged the One Ring in Mount Doom without Celebrimbor's knowledge.

 

"The Three, fairest of all, the Elf-lords hid from him, and his hand never touched them or sullied them.  Seven the Dwarf-kings possessed, but three he has recovered, and the others the dragons have consumed.   Nine he gave to Mortal Men, proud and great, and so ensnared them.  Long ago they fell under the dominion of the One, and they became Ringwraiths, shadows under his great Shadow, his most terrible servants...He only needs the One; for he made that Ring himself, it is his, and he let a great part of his own former power pass into it, so he could rule all the others." ~The Fellowship of the Ring, Book I, chap. 2 (The Shadow of the Past)