Porta Orientalis is their Roman name. These gates were used to enter the palace from the east towards the west, through the main street, decumanus, all the way to the Iron Gate and to Pjaca, the central city square.
The Silver Gate was more modest in its decorations than the Golden one, and it was closed from the Middle Ages till 1952, only to be thoroughly reconstructed during the destruction of the Baroque church Dušica. On each side of the gate, the remains of the octagonal towers are visible, hence making it easy to imagine the beauty of the construction and the strength of the control over the entrances from the north, east and west. Entering through those gates the passersby, even today, have the opportunity to walk the original ancient pavement on decumanus, walked also, so many years ago, by the Diocletian's subjects.
Silver Gate has recently enriched its history with the greatest event for all the Split Catholics when in the year 2000 Pope John Paul II passed through them admiring the beauty of St Domniuses Cathedral where he later prayed.
https://visitsplit.com/en/522/the-silver-gate