A gentle shaking of either minaret results in the other minaret vibrating after a few seconds,  though the connecting passage between them remains free of vibration. The mechanism of this is not known, although the layered construction is thought to be a factor.
When either minaret is gently shaken, the other one vibrates after several seconds, but the passage between them does not vibrate.  The cause of this effect is unclear, though the layered structure of the minarets may play a role.