Most beautiful 1 day hike?

[javago]

Hi Serbia experts,
1 more question, молим
My future Serbia trip includes a monday, (Sep05), when most museums are closed.
That's why I would like to leave Belgrade for a one day hike in nature.
Preferably to the nicest mountain or canyon/gorge in the country!
It has to be reachable from Belgrade with bus or train.
Any suggestions?
Hvala puno, Живели
Jan

[Vilenjak]

The most beautiful pleases are far away from Belgrad.

You can find something in Avala mountain or in the city. Kosutnjak and Ratno Ostrvo.