Rosenvold is the Alving's estate on the west coast of Norway. It is remote, encompassed by mountains and fjords, and enshrouded in rain. In October, for example, there's precipitation 25 days of the month. Think Seattle, but colder. By setting the play in Norway, Ibsen highlights the contrast between a duty-bound life in the North and the life-loving ethos in southern places like Paris. Check out "Location" in "Character Clues" for more on this.
Ibsen doesn't specify the year, but we can assume Ghosts takes place in the late 19th century. You know that Victorian rap: propriety is important and your reputation is everything. Get married. Premarital sex? Don't do it (girls). Divorce? Not an option. The main thing is to keep your business to yourself. These principles are all at work in Ghosts.
All of the action we see happens in the same place. It's a big garden-room with three doors leading upstairs, to the kitchen, and to the garden. Furniture-wise, there are two important pieces: a round table covered with books and periodicals, and a sofa with a little worktable. This is Mrs. Alving's house – she lives here alone now, except for the servant Regina – and these two furniture pieces give us clues about her divided character. The round table, with its evidence of a voracious reader, shows us the intellectually curious, and progressive Mrs. Alving. At the sofa and worktable, the domestic, and motherly Mrs. Alving sits when she's knitting or doing needlework. We'll see these two Mrs. Alvings have it out with each other, all within the confines of this room.
The back of the room attaches to a greenhouse, and through its glass wall we see the outdoors. Ghosts begins with a gloomy fjord landscape that doesn't let up until the very last minutes of the play. To see more about why Ibsen made the weather such a prominent feature of the setting, check out to "Symbols, Imagery, Allegory."