Thornfield is imposing from the outside and Jane is intimated by its looming presence, but when she enters, she finds it not as bad as she'd feared.
This description of her initial entry to Thornfield is found in Chapter 11, about two-three pages in, in my text:
"...the driver got down and opened a pair of gates: we passed through, and they clashed to behind us. We now slowly ascended a drive, and came upon the long front of a house; candlelight gleamed from one of the curtained bow-window; all the rest were dark.
"Will you walk this way, ma'am?" said the girl, and I followed her across a square hall with high doors all round: she ushered me into a room whose double illuimation of fire and candle first dazzled me, contrasting as it did with the darkness...when I could see, however, a cosy and agreebale picture presented itself to my view.
A snug small room; a round table by a cheerful fire; an arm-chair, high-backed and old-fashioned..."
Jane also notices that Thornfield is three stories high and of considerable size, befitting the house of a gentleman. She describes it as "picturesque" with "battlements round the top" and a grey front.
On the inside, Jane notices the oak steps and banisters and the high, latticed window of the stairs. She says the window and the long gallery "looked as if they belonged to a church rather than a house". She sees the pictures on the walls of a man and woman, probably ancestors, a bronze light hanging from the ceiling, and a clock with an oak case that is "curiously carved". The hall door is half glass.
Her room has blue chintz curtains, wallpaper, and carpet on the floor, furnished in an "ordinary, modern style". She feels she is safe once she's in her room.