3 adjectives to describe inaccessibility

What they have really done is to prove that there exists a narrow line by which a way may be found to the top of any given mountain; but the clue leads through innumerable inaccessibilities; true, you can follow one path, but to right and left are cliffs which no human foot will ever tread, and whose terrors can only be realised when you are in their immediate neighbourhood.

" She listened, discouraged yet fascinated by his sturdy inaccessibility to all her arguments and objections.

The enormous extent of the frontier dividing the white settler from the savage, and the tangled inaccessibility of the country in which it everywhere lay, rendered it as difficult for the national authorities to control the frontiersmen as it was to chastise the Indians.

3 adjectives to describe  inaccessibility