The dawn breaks early in Pittsburgh, sometime around 5. The birds know this. So do light sleepers.

Ordinarily I love the sound of birds in the morning, their airy, atonal notes, never the same, their optimistic spirits, always ready to soldier on. A nice way to start the day.

But this morning I hear their songs, right on time, and I’m unsettled. This morning their offering, their presence, is not enough. Something is missing.

A day after visiting Frank Lloyd Wright’s Fallingwater, called by some America’s most extraordinary house,  I awake expecting to hear the sound of water, falling water, gushing water. Where, I think in my subconscious brain, still not fully engaged, where is the water?

I have seen pictures of the house, some two hours east of Pittsburgh, although for some reason Pittsburgh is rarely mentioned in the description; it’s always Bear Run, as if we know where that is. I have visited another Frank Lloyd Wright house outside Scottsdale, Ariz., but it’s in the desert and the day was hot, too hot to concentrate on architecture.

I have read about E.J. Kaufmann, the Renaissance-like owner of Fallingwater who married his first cousin, some say to get closer in line to the family business with the same name, a venerable downtown Pittsburgh department store recently taken over by Macy’s.

I know from a brief but intense infatuation/flirtation with author Ayn Rand -- but have forgotten until this week -- that her memorable character Howard Roark, of  The Fountainhead, is based on Wright.

But to make the drive on the Pennsylvania Turnpike, past Normalville (unfortunately the sign was removed a few years ago) and Greensburg (named in part for Gen. Nathanael Greene, whose remains rest in Savannah’s Johnson Square), then to take the short walk into the darkly wooded grounds past the press of rhododendron and the primordial presence of ferns and to see the spreading, horizontal house built directly into the hillside, perched over a pummeting waterfall which rushes, 24/7, inches below a terrace is something else altogether.

It’s one thing to be rich, like the Kaufmanns. It’s another to travel the world and to buy art -- which they turned around and displayed in galleries in their department store, partially as fans of art, partially as a way to get people to come into the store.

Still another to leave as a legacy to your town magnificently designed houses and buildings, which people used to do because they loved where they lived and wanted to give something back.

But it’s quite another in the mid-1930’s for the Kaufmanns to engage the likes of Frank Lloyd Wright -- not all that receptive to Jews to boot -- to build them a weekend getaway in the woods, without power tools, without computer mockups, without the easiest of transportation choices to get the materials and themselves there and back. And then there’s the matter of finding trust in the architect’s plans, an architect who by that time was in a veritable slump of his own.

“We like the waterfall,” they must have said, never expecting a house designed to be built on top of the waterfall.

I mean, there we gather in the woods, people of the 21st century, looking at the three large stone ledges or floors protruding into air, hearing about the 41-and-a-half-foot chimney as the spine of the house and the strongest vertical support  and collectively we wonder: How does the thing stand up? Why doesn’t it fall down?

Our guide tries to use the concept of diving boards as a way to explain the cantilevered and concreted balconies. We know about diving boards. We try to make the leap to concrete roofs and floors with nothing holding them up, but before we can get there our trusty guide is pointing to the rock ledge next to the fireplace in the open living room and asking, “So are we inside or outside? Where is in and where is out?”

While we contemplate this she really blows our mind by telling us Wright, born in 1867, designed this house when he was 68.

Now for the kicker: After he finished Fallingwater, he went on to design 200 more houses until he died at age 92.

By then, she is telling us about the limestone floors. Wright wanted them polished to invite the water into the house. But he compromised on the chairs, choosing three-legged varieties to accommodate the uneven surface of the limestone. In the guest quarters the room is deliberately small and the ceiling deliberately low because Wright wanted “to direct our eye outside” to the woods, to the water.

While we try to visualize this she opens and closes one of the 17 windows stacked in a vertical column to demonstrate Wright’s idea of “volume control” of the waterfall. She points to the steps leading down to the waterfall through a glass gate, visible through a series of glass windows.

Again, the water.  It all comes back to the water. It’ll be awhile before I forget standing in a house and hearing the the rush of water.