In Villachula, you will the emporium and need the dimension swap and pollo slide to enter another dimension. It is recommended that you have 1300 coins before doing this. Enter this dimension and approach the closed doors on the left. The family will say that they are trapped inside. You can unlock the door by paying 10 gold and opening the doors. Once inside the father will allow you to take the reward behind the silver gate. You must pay 100 gold to open the gate. Once inside, you will see a giant chest. You can open it for 250 gold. Inside is a smaller silver chest. You can open it for 800 gold. Once opened, you will receive 1 gold and the achievement will pop.