I suggest [The House on the Borderland][1] (1908) by William Hope Hodgson.

From the Wikipedia description: 

> Two men on **a two-week fishing vacation** in remote western Ireland are
> surprised to discover **a strange abyss**. On a rock spur above this pit
> they find **ruins** and buried in them **a journal, which they read**.

[more details coming]


  [1]: https://www.goodreads.com/book/show/220937.The_House_on_the_Borderland?from_search=true&from_srp=true&qid=7jzjNz45Tn&rank=1