The facility is constructed around the light of the fluttering heart.
The heart is a mass of filmy, translucent sheets, bundled loosely together around the central light source. The sheets wave in the shifting light like flags in the wind, casting wavering half-shadows over the facility.
Long steel spikes extend inward from the facility. The sheets move around and against them: sometimes a sheet is pinned against one of the steel columns, draped and flapping; sometimes a sheet slides over, across, and past one; sometimes a sheet barely brushes a column as it flutters past.
In the heart's dimmer hours, when the fluttering of the sheets has slowed to a murmur, the staff of the facility climb down the long ladders bolted to the side of the spikes, and they attempt to move the sheets by hand. Slowly they gather the enormous fabric, pulling it by yards out of the way of the long columns. Some shifts, they reach the end of a sheet before the light begins to grow and the klaxon sounds to retreat, and the column extends another few feet towards the center of the heart.
After such an extension, the waxing light carries with it a sound not heard elsewhere, a deep rumbling vibration from the center of the heart. The sound is officially called a "hum". When the staff are out of earshot of the bosses, whispering their unlicensed rumors, they say that it is the groaning of heartburn. The heart is in pain, they say; it is angry; it will soon catch fire; it will wake up; it will die. These rumors, varied and wild and contradictory, have existed since the first extension and the first hum, and none have ever come true. Yet still the rumors persist.
Gradually, the facility progresses inward, seeking the heart of the heart.
(Clarification: the Slowlands setting is canon for this, but not necessarily vice versa. It might be considered a fork, or autofanfiction.)