I used a flytrap mansion with some success when I DM:ed CoC a couple of years back.

The first night that the pc:s slept in the manor they were trapped in what was actually a dreamreflection of the building and a bit of its surroundings. Unaware that it was a dream they continued conductiong the investigation around the house.

If they walked away from the house they would eventually come back to it from another direction. After adding the feeling of having something stalking them as soon as they left the manor the pc:s refused to leave the house and actually barricaded the doors and windows.