Question about Dol Guldor.

Does anyone know if Dol Guldor was built by Sauron, or did he simply take over an existing structure (similar to what Saruman did with Orthanc). If so, who built and watched over the structure before it was abandoned?

Wow, do I wish I had the old MERP Dol Guldor supplement:D

Thanks,
Reptile

Dol Guldur is a creation entirely of Sauron, though it has little, if any, real description in any sources. Sauron simply found the hill of Amon Lanc and reared a fortress for himelf.

Robert Foster's The Complete Guide to Middle Earth guesses that Dol Guldur was built by Sauron in TA 1050 and the Wise became aware of a dark power there in 1100.

THanks guys.