A semi fisheye or very wide angle may work for you, but you may well be better off using an edge-of-wideangle lens and panorama stitching or virtual tour software. Very wide angle lenses will invariably introduce what the eye/brain see as distortion. A panorame can be made to feel more normal even if it is effectively introducing distortions of its own (eg mapping time variant angular rotation on to a linear plane).
As one example, panorama software from Autostitch is free and marvellous, and commercial offerings using it add to it's basic functionality.
Autostitch free download here
See that website for links to commercial versions - but the free version may do what you want.
Here is one of several impressive demonstrations - zoom right out and use cursor keys to rotate continually or tilt vertically.
Also look at possibly using a mirrorball type lens such as Heather discussed recently in this answer - [NOT a duplicate btw]
End result looks much better than what you see here.