24-hours in Nis and Belgrade

A friend of mine, let's call her Madam J, is going to Serbia soon. A no, she's not a diplomat nor of Serbian origin, she's just smart and worldly, and can smell fun.
So, she made me think about what I love to do in Belgrade and Nis, when I'm there just for a day or two.
Belgrade. Hmmm. Let's see what comes in mind.
I love the stroll from Slavija to Terazije, and along Knez Mihajlova, of course.
I love stopping at Greenet in Nusiceva street and having a small moka there. (Picture attached)
If I happen to be in Terazije in the evening, Ben Akuba, also on Nusiceva, makes the best cocktails, and it's hidden in an apartment, and looks like something out of a novel, dark, with books on shelves against the walls, and menus with nothing but cocktails.

In Nis, I like the walk along Pobedina street, and stopping for a drink in Kazandzijsko Sokace, or in one of the cafes along Pobedina, or even Costa Coffee on the main square, with a great view of the square and people walking toward and away in every direction.
I love having a cheap but excellent horseback riding lesson in Konjicki Klub Nis, close to Niska Banja, and then going to the Spa in Niska Banja, in Radon hotel, for a jacuzzi and a massage, all very affordable for U.S. standards.
But she'll be there around St. Nikola's Slava. So the best thing to do is to befriend a Serb, and go to as many Slavas as possible.