On 30 panels, visitors will be able to see the events that preceded the handing over of the keys, the act of surrender (April 6/19, 1867, at the site of today's memorial in the Kalemegdan Park a firman issued by Sultan Abdul Aziz was read in Belgrade according to which the fortresses of Šabac, Smederevo and Kladovo were to be handed over to the authority of the Serbs), as well as the consequences of this event for the Serbs.