Seshat's Grotto
The easiest way to find this one is by following the marker for the The Killer Shadow side quest.
There's a pair of guards to the south as you enter the passage. You can snipe them, ignite the hay at their feet, or whistle one over and chainkill the other, but whatever you chose, they both need to die.
When they're gone, smash open the wooden panel in the right corner behind them.
This leads to a small cavern of child slaves. Before seeing to their plight, you might check out the south end of the cave, where both location treasures can be found.
Looting both completes the location.