After you've eaten at Esurient's Mother's house in Avence Town, you can enter Toronko Ruins.
Toronko Ruins is southeast of Avence Town.
When you enter the ruins, talk to Esurient (the guard). He smells the scent of his mom's cooking on your clothes, and it makes him so hungry that he leaves his post (after you offer to stand guard in his place, which, of course, you don't do).
After the dialogue, take the secret passage on the east side of the entrance to get a treasure. Now go north through the door, and take the secret passage on the west side of the path to get another treasure.
Now, take the exit to the east to get to a side room with one treasure. Now go back to the entrance and take the west exit to the first screen.