My father-in-law had gone away on holiday and organised for the furniture in his living room to be sent for recovering. My husband and I went every morning to the house to open up windows and curtains and returned in the evening to close the windows and curtains. On one occasion we walked into the room and near the centre discovered a 'patch' that was colder than the rest of the room. We investigated by moving around and going in and out of the 'cube', reaching up our arms to see if the air was warmer above a certain height and trying to find a shape for the phenomena. it was a definite cube about 6 ft square and six feet high. As we moved around it became colder and colder.
The month was December and the weather was hot and humid. The temperature often reaches 35 degrees or more. The temperature in the 'cube' was icy!
We went about closing windows - although neither of us wanted to go down the passage alone - and left the house before dusk!
It was an extremely creepy experience.
Some year or so later we moved into this same house but never experienced the cube of ice again.