Disclaimer: I am not J. K. Rowling. I do not own Harry Potter.
Note: The following is by way of an experimental attempt to nail down some details of geography and history of Hogwarts for the 'Saint Potter' alternate universe. See author notes for more on this, but some details will almost certainly differ from canon. This piece is rated 'T'.
Further Note: The piece is an account dictated in the late twentieth century by an 'in universe' character, who has their own views and agenda, and may be biased, guessing, or otherwise misleading on some points.
Revision (14th March, 2016): Minor rewording and expansion of text of this chapter.
Extract From 'Aquinas' Guide to Hogwarts'
Quite what possessed the four 'founders' – Godric Gryffindor, Helga Hufflepuff, Rowena Ravenclaw and Salazar Slytherin – to establish a base of operations which was subsequently to become a school of magic in a remote Scottish glen is, due to the lack of credible historic sources on the matter, a topic for endless debate. The man that most sources tell us was the leader in this enterprise, Godric, was a west-country man from England, and so the decision to go quite so far from the lands in which he was commonly travelled – and had known from birth – at face value seems to make little sense. Although England was occasionally riven by struggles between the Anglo-Saxons and the Norsemen at the time, Scotland was itself hardly free from incidents – though given the way that muggles of the time generally avoided areas such as what has since become known as 'The Forbidden Forest' (itself considerably more extensive in that era), it is possible that the positioning of Hogwarts in what at the time was the midst of the forest may have offered a shield against most muggle intrusions. Another possibility is that the founders deliberately sought out the location with a view to trading with the centaurs in said forest for rare animal parts and plants that the centaurs had ready access to in the forest, and perhaps also with the merfolk of the lake. And then there are wilder theories, such as that Hogwarts was built close to or on the site of Rowena's home, and that she, being an enchantress of great wiles and subtle magic, beguiled Godric into abandoning the lands that he knew to travel so far north to settle, for her own convenience. In the opinion of this author, such latter stories are sufficiently insulting to Godric's abilities as a wizard – and as a man who knew his own mind – as to be worth mentioning only to display their obvious ridiculousness. And then there are the crazy theories that the land which was in later centuries to come to be occupied by Hogsmeade was the site of a meteorite strike, and that the founders travelled all the way to Scotland to establish a fortress nearby for convenience of study of it (or due to more superstitious reasons pertaining to its presence)…
At any rate, whatever their reasons for choosing the site, the four founders travelled to Scotland and in the middle of the Forbidden Forest, on a narrow neck of land betwixt mountains and lake, raised their fortress.
And Hogwarts, at founding, was a fortress. The keep, facing towards the heart of the forest, and the great hall 'sheltered' to the southwest in its 'lee', built with the aid of giants (either conscripted or in alliance with Godric, depending on which accounts you believe), was unquestionably first and foremost the seat of a warlord. It may have been that Godric meant merely to deter giving an impression of weakness to his new neighbours, which might lead to trouble, but the shifting staircases, capricious doors, hidden chambers, and shifting 'dead ends' of the original buildings are all features of a residence constructed for the purpose of giving the occupiers as much advantage as humanly possible to achieve over any invader, should battle ever arise. Indeed, during the first winter of construction at the site, an unsuccessful attack on the construction work was made by a militant faction of the centaurs of the forest and a number of creatures which they had either pressed into service or temporary allied with. This treacherous attack, made during the day of the Yule feast, when the centaurs hoped to catch the witches and wizards off their guard and making merry, was beaten off at bloody and terrible cost to the forces of the forest, whose plan was not, due to the superbness of Godric's spymaster, the surprise that they had hoped it to be. It was not to be the last attack upon Hogwarts by enemies, least of all from those living normally within the surrounding forest, but as it subsequently turned out it was sufficient to guarantee peaceful co-existence with the forest-dwellers for the rest of the duration of the original four founders' occupation of the site. (Perhaps Godric's hurried expansion of his planned works to include an additional tower abutting the northwest side of the keep, to serve as a barracks block for muggle mercenaries may have contributed too…)
As of April 2014, I have been unable to find definitive information on several points of the history, geography, or location of canon Hogwarts - so have taken to reinventing canon or finding my own answers altogether, for the purposes of background of the 'Saint Potter' alternate universe.
In the 'Saint Potter' universe, Hogwarts is positioned close to the northeast 'toe' of Beinn Bheòil, and Loch Ericht is assumed to be much smaller and to constitute 'The Black Lake'. (Land which in the real world is otherwise occupied by Loch Ericht is assumed in the 'Saint Potter' universe to be for the greater part occupied by 'The Forbidden Forest', which also extends over most of the real world 'catchment' area of Loch Ericht, and also over the upper reaches of the nearby River Pattack.
By 1991, in the Saint Potter universe, Godric's original 'keep' has become for the most part staff & guest accommodation, and the 'barracks' ended up becoming Ravenclaw Tower. Other parts were added to the school and/or adapted over the centuries.
Update: (24th April, 2014)
In the next instalment I take a line that the initial buildings were known as 'Godric's Keep'; the 'Hogwarts' name came later, after it had become a school.