One of the locations mentioned in Merlin's prophecy where King Arthur and his knights embarked on a quest to seek out the Sangraal, also known as the Bloodstone. The land is a great distance from Camelot. (It is believed he also searched for the device in Castiana and Vagonbrei.)
Sahal was once inhabited -- likely by the Ancients -- but today only the remains of stone structures remain to be found. They were likely abandoned some 40,000 years ago.
HOME TO - Uninhabited
FIRST APPEARED - N/A
Camelot - Meurik tells Mitchell and Jackson of Arthur's quest to seek out Castiana, Sahal and Vagonbrei.
The Pegasus Project - SG-1 visits Atlantis to try and find coordinates to Castiana and Sahal, and encounter an ascended Morgan Le Fay.
Insiders - Colonel Carter reports that only ruins were found on Sahal, but no evidence of the Sangraal.
The Quest, Part 1 - Daniel and Vala discover that Sahal's gate address is only one part of a puzzle that will lead them to the Sangraal.