Gate to Old Vizima

From Witcher Wiki

Depending on which side of it you find yourself, this is either the Old Vizima Gate or the Gate to the Dike. It is one of the last sights that many an unfortunate plague victim sees as it is their last stop, after St. Lebioda's Hospital, and before the cemetery.

In Acts II and III, the gate is visible on the dike, but locked for the duration of both Acts. In Act V, Geralt passes through it after a skirmish on the dike, on his way to find Shani who has set up the field hospital to help victims of the fighting which has spilled into the streets.