On day one of our exile, we met Bruno who told us about a "stone house with stone walls" located 13-14 miles north of where we started. Our group of 114 left the Portal and arrived at the castle by evening. There were occasional trees in the area, and a mountain about 10-15 miles directly west. We investigated the castle and found that the previous occupants had died, many died near the same time based on the dates in the mausoleum, although the dates did not seem to correspond to our calendar system. They had already been reduced to skeletons. The skeletons didn't appear to have any weapon marks on their bones. Tattered tapestries lined the walls, and the castle appeared to have rotted and wasted away overall. It did appear to be quite well insulated. We found an apparently one-way portal drawn in blue blood on the floor, and a massive storage room with about 50 BP of supplies in the basement, including some unspoiled food. There was what appeared to be an everflowing spring with water coming out of what looked like dwarf heads; a knowledge (local) check established that the water was safe to drink. We slept the night without incident, and were able to load 10 BP onto our wagons for our trip West to the green land.
When we returned to the castle, we found that the magic circle was gone, and the skeletons had been cleaned away, presumably by Jebediah.
The castle throne room lies in the middle of the courtyard. It has a front door, back door, and a chimney. It has a main hall with enough torch stands for it to be well-lit.