Boiling Water Bath

A cylinder with a movable piston is placed in an ice water bath and is in thermal equilibrium. The cylinder is then removed from the ice water and placed in boiling water. After the system reaches its thermal equilibrium, the final pressure is the same as in the ice water bath. I do not understand why.

Any help? Thank you!

is the movable piston changed location to compensate for the pressure, or inside the cylinder was in the vacuum each time.