To find Turrfield's buried treasure, you first have to talk to a little girl. It is located in the northwestern part of the city, where Sonya showed you the big drawing on the hill.
The little girl's riddle
'Seek yourself three standing stones, with Grass before the other ones. Use well that Strength, and find then the strength of its strength in the end. Dally not, if you’ve a mind to find what time has left behind.'
We understand that the answer to the riddle is Fire. But where do we go next?
You will notice that Turrfield is surrounded by Runes marked stones. These Runes represent the types.
How to find the treasure
Each of the Turrfield Stones represents a type. You must touch the stones in the right order: Grass - Water - Fire.
1. Touch the Stone which is located to the right of the little girl, at the bottom (next to the florist)
2. The Stone symbolizing Water is located on the left of the little girl, where a man stands in front of her.
3. Now you can activate the Fire Stone which is located just east of Turffield.
You will then obtain the Expert Belt. It is an item that increases the power of Super Effective moves.
Tip: if it doesn't work, you have to get out of the city and try again.