"Widzisz horyzont?"

Translation: Do you see the horizon?

[Volizione]

Are "widnokrąg" and "nieboskłon" completely synonymous with "horyzont?"

[immery]

nieboskłon is a "surface" of sky. (the lower part)-http://sjp.pwn.pl/szukaj/nieboskłon.html

widnokręg is literal perceived line of sky meating with eath/sea http://sjp.pwn.pl/slowniki/widnokrąg.html

horyzont has also figurative meanings http://sjp.pwn.pl/szukaj/horyzont.html

[Volizione]

Thank you for your explanation.