This is the only remaining gate of the original nine built in the 16c. The others were later pulled down by the government in the 18c. It’s also been called the Medininkai Gate.
On the other side there is a chapel of Our Lady of the Gate of Dawn with an icon of the Virgin Mary, painted in the 17c and also called the Vilnius Madonna, which attracts pilgrims from all over Europe.
Lithuania was the last European country to covert to christianity and if you look carefully at the gate you will see that they still seem to be hedging their bets about whom to serve.
At the very top is a figure representing the Grand Duke and in the window frame below there is a painting of Christ. However if you look just below the cornice beneath the mounted Duke you will see a pagan face which I think is Hermes.