Do you remember a path from blacksmith Andrei to the bonfire in Darkroot Garden? There was a possibility to turn right in this place:
At a first glances this slope looks too steep - but if you look closer, you'll find a descent down. Follow it closely. The path is winding.
At some point you'll get to the junction.
It is best to go to the rocky ledge on the left. At its end you can jump down and pick up Leather armor and Longbow.
After collecting these items, jump one more level down and run forwards.
You'll get to a larger passage between hills (to the left). In front of you, you will see a tower, which can be accessed with Watchtower Basement Key. Inside you'll find a dangerous enemy - Havel, who possesses important items. During the fight you can't get hit not even once. This requires a perfect mastery of dodges - when the enemy strikes from above his head, jump behind his back and hit him with a special attack from behind.
A path to the left, through a larger passage, leads to the lake and Hydra (a method o defeating her is described in a chapter about bosses). Before you fight with her, you have to eliminate crystal golems, luring them with a bow if needed. You can now walk alongside the lake and take a turn to the left. Fight the Golden Golem. If you win, the girl will be free. Talk to her and answer her question affirmatively. Return here after you have obtained the necklace at Duke's Archives. Touch to the black mist and travel to Sanctuary Oolacile from the Artorias Of The Abyss DLC.
Form this place you go down with another winding path. It is guarded by a knight with a shield and a spear. You might lure him to the wider edge of a slope, so you won't fall down. During the fight try to keep at his back and block his blows.
Below you'll find an item - Grass Crest Shield.
On the other side of the rocky ledge you'll find a cavern with a bonfire inside
Behind the bonfire, there is an elevator which leads to Valley of the Drakes.