Near skopje there's a national park called Matka Canyon. It's a 45 minute bus ride, so a bit of a pain to get there, but due to recent changes in laws, bus drivers don't bother selling tickets because it is a pain for them, so I got a free round trip as both drivers said no. It's a huge canyon with a dammed up river so there's a big man made lake. There are also caves. You can hire a boat to take you to the caves or kayak there. I decided to kayak there. Long kayak ride. Caves were beautiful though small. That was most of my day. I also got dinner somewhere. Cheese covered sausage. Really really good.