2. The bridge
The bridge swings over the stream "with ease and power." It does not just connect banks that are already there The banks emerge as banks only as the bridge crosses the stream. The bridge designedly causes them to lie across from each other.
One side is set off against the other by the bridge. Nor do the banks stretch along the stream as indifferent border strips of the dry land. With the banks, the bridge brings to the stream the one and the other expanse of the landscape lying behind them.
The bridge gathers the earth as landscape around the stream. Thus it guides and attends the stream through the meadows. Resting upright in the stream's bed, the bridge-piers bear the swing of the arches that leave the stream's waters to run their course...
The bridge lets the stream run its course and at the same time grants their way to mortals so that they may come and go from shore to shore.
Bridges lead in many ways. The city bridge leads from the precincts of the castle to the cathedral square; the river bridge near the country town brings wagons and horse teams to the surrounding villages. The old stone bridge's humble brook crossing gives to the harvest wagon its passage from the fields into the village and carries the lumber cart from the field path to the road. The highway bridge is tied into the network of long-distance traffic, paced as calculated for maximum yield...
The bridge gathers, as a passage that crosses, before the divinities -- whether we explicitly think of, and visibly give thanks for, their presence, as in the figure of the saint of the bridge, or whether that divine presence is obstructed or even pushed wholly aside.
The bridge gathers to itself in its own way earth and sky, divinities and mortals.
Heidegger, "Building Dwelling Thinking"
What is he trying to say here? Does the bridge "make" the landscape? In an important sense, it does. The land, and river, are pure potential, and as such are latent. We don't see the either the human or the natural potential here. But with the bridge, potential is uncovered. We can see a life.
So what kind of life is it? For humans, one that takes the river into account. The river makes some things possible (e.g., shipping, fishing), and in other ways complicates things (e.g., it might overflow, freeze, become polluted). But the life by a river is a particular kind of life, just as Maritime fishing communities are particular kinds of communities because of their relationship to the sea. They too have a technology - boats, rather than bridges, but the same thing applies. What they have built opens up a relationship between themselves and nature.
The bridge "gathers together" the river. A bridge creates a location.