His house is known as the

Bilbo's house is known as The Hill.

It had a perfectly round door like a porthole, painted green, with a shiny yellow brass knob in the exact middle. The door opened on to a tube-shaped hall like a tunnel: a very comfortable tunnel without smoke, with panelled walls, and floors tiled and carpeted, provided with polished chairs, and lots and lots of pegs for hats and coats - the hobbit was fond of visitors. The tunnel wound on and on, going fairly but not quite straight into the side of the hill - The Hill, as all the people for many miles round called it - and many little round doors opened out of it, first on one side and then on another.