The expression "promised landscapes" originates on a quote of Ortega from Prólogo para alemanes, a text of 1934: "all people have inside them a promised landscape and roams the face of the earth like a pilgrim until it is found". The promised landscape was for Ortega -or so it seems- a variable promised land, this is, the metaphor of a collective ideal, of a national ideal.
The possible historical use of the term "landscape" in this quote, is not in the sense I would initially apply it. "Promised landscapes" -a very fortunate expression if you ask me, and very representative of Ortega- is from my historian perspective an excuse to analyze the historical topics in a certain geographical location: a place, a city, a district, a region. Ortega himself used to say that landscapes had built half of his soul. And it is like that -consciously or unconsciously- for many of us. The landscape, the aesthetical beauty of nature (there is no ugly landscape, as Unamuno said), or our own rural or urban environment created by man along the centuries, are indeed the place of our first and original installment in life -and for this, in most occasions it becomes unforgettable for the rest of our life-. The place of our social and political circumstances (our "homeland", as Ortega himself would say), the main object, if not obsession, of our worries and conscience. In any case, landscapes can trigger the meditation of historians (and even more for geographers, of course, for whom the landscape is not an invitation, like for historians, but an obligation).
Thus, the approach of historians to landscapes is a way of making history. Landscapes have indeed a historical significance: they are mythical, legendary, imperial, religious, philosophic, literary, political or national (among other) places. They are always a scene or theatre for different situations, which is decisively important for a historian (a concept of history that Sartre used). Thus, by elucidating a landscape we may be capable to get into the history of a country.
As it is logic, this requires to "create" categories that turn a simple location into a "promised landscape". The categories could be: accused specificity; historical significance; symbolic and imaginary value; literary-essay dimension; relevant interpretation (or interpretations), historiographic if possible. For purely pedagogic reasons allow me to put an easily recognizable and understandable example: The American Wild West. The Wild West would thus have: 1) a unique geography, specific and pronounced: always great landscapes, colossal, such as the great prairies or the Rocky Mountains, or the rivers Bravo, Grande and Missouri, and some times desert and haunting like Death Valley, or Monument Valley, or the Great Canyon; and within them, there are legendary sites: Tombstone, scenario of the Gunfight at the O.K. Corral, Tucson, Abilene, Fort Laramie, or Little Big Horn, the location where June 25th 1876 Custer and his 250 soldiers where killed by a feisty force of indians commanded by Crazy Horse...; 2) historical significance: the expansion to the West between 1840 and 1890, linked to the railroad, agriculture, ranching, new states and indian wars, as a key historical period for the United States of America; 3) symbolic and imaginary value: The West, with epic violence, justice and freedom, as a heroic period; 4) literary-essay dimension: but especially cinematographic, a legacy of myths and semi-heroes (redeemers, gunslingers, outlaws, cowboys, sheriffs, indians, cavalry): Billy The Kid, Jesse James, Wyatt Earp, Pat Garret, General Custer, Sitting Bull, Crazy Horse, Cochise, Geronimo..., names like those in Homer's Iliad.