The architecture of the house is indeterminate, and actually changes periodically. The same holds true for the inside of the house: the rooms shift about, and one never enters the same room twice. Due to the fact that so many stories were inspired and relayed within the rooms of the old home, the House of Secrets is a focal location at the crossroads into the Dreaming. The Dream Lord was able to access the House of Secrets at will without manifesting inside the mind of a sleeping individual.
Abel lives there with his gargoyle, Goldie, and it was this house that Dream was able to reach upon his return to the Dreaming after his incarceration in the waking world. He was found and dropped on the doorstep by Cain's gargoyle, Gregory. Cain promised him to "have you back on your feet again."
It was from The House of Secrets Dream made his way to the heart of the Dreaming to find it devastated.