What is the dictionary form of "bliska" in "z bliska".
What is the dictionary form of "bliska" in the following sentence?

Obserwowałem ich z bliska.

As I know, "z" is followed by genitive or instrumental case noun.
If "bliska" is a genitive case, there must be a word like "blisk" or "blisko".
I cannot find a word "blisk" in dictionary.
I can find a word "blisko". But it is an adverb.
By any chance, can "blisko" be a noun?

Question

What is the dictionary form of "bliska" in "z bliska".
What is the dictionary form of "bliska" in the following sentence?

Obserwowałem ich z bliska.

As I know, "z" is followed by genitive or instrumental case noun.
If "bliska" is a genitive case, there must be a word like "blisk" or "blisko".
I cannot find a word "blisk" in dictionary.
I can find a word "blisko". But it is an adverb.
By any chance, can "blisko" be a noun?

Answer

It is adverb "blisko".

We have a class of adverbs calls przysłówki odprzymiotnikowe (adverbs-from-adjectives) and Przysłówki odprzymiotnikowe  looks like specific form of adjectives. We have a few groups of them:  przysłówki jakości (e.g ładnie, brzydko), sposobu (e.g ręcznie, pieszo, maszynowo), stopnia (e.g często, sporadycznie), aspektu (e.g literacko, malowniczo), czasu (dawno, współcześnie) i miejsca (daleko, blisko, wysoko, głęboko). Adjectives, which are out of these groups don't have adverbs form.

Answer

The dictionary form of "z bliska" is "bliski", which is an adjective. 
But I don't know if it makes sense considering the rules, because I don't know them. Sorry ^^"

Answer

"Blisko" is an adverb. This phrase is like idiom. We don't have in polish noun "blisk" or "blisko" :)
It is a similar situation with antonim "daleko" - "Obserwowałem ich z daleka"