What are the gothic features in Rappaccini's daughter?

"Rappaccini's Daughter" is a 1844 short story by Nathaniel Hawthorne, written at a period in which Romantic or Gothic story writing was flourishing. It has several Gothic elements, described below.
The first Gothic element is one of an exotic setting. It was set in Padua, Italy in some unspecified period of the past, and thus would have appeared exotic to its American readers.
Next, there is the house with its association with the aristocracy and the mysterious doctor skilled in arcane knowledge. The protagonist and other major characters are distinguished by their extraordinary nature: the two scientists by their brilliance and the two young people by their physical beauty.
The protagonist through whose eyes we see the story is an innocent who only gradually begins to understand the evil surrounding him, despite a significant number of warnings or foreshadowings. This helps to create the typically Gothic foreboding atmosphere.
Finally, the narrator routinely uses adjectives and other descriptive devices to enhance to sense of lurking evil or menace. He describes the lodging room as "a high and gloomy chamber of an old edifice" and immediately suggests that the house itself once belonged to a family, including one of the evil aristocrats who appears in Hell in Dante's Inferno.