Mezyn National Nature Park was founded in 2006 by decree of President Viktor Yushchenko. In the last year of his reign, the President created many national parks, or increased the funding for existing ones.
On this territory, archaeologists found houses of ancient people who had been living here 20 thousand years BC (information in English). They found many mammoth bones, most of which were taken to the major museums of Kyiv, New York and Europe. Besides, a lot of tools, jewelry, household goods and other items were found. Many of them are presented in the local museum.
But most important, the park offers stunning views from the high banks of the Desna river (map in Ukrainian and the same place on Google Maps), which can attract mass tourists (of course, if the government makes normal roads). In spring the water is incredibly high.
Near the Sverdlovka village on the high banks of the Desna river stands quite an unusual house for this area (here). This beautiful cottage was used by ex-president Leonid Kuchma as a place for the rest. He was coming there by helicopter.
Near the gazebo we found a large number of snakes that had a "wedding". However, the shutter sound prevented them a little :)
By the way, there's a lot of animals here. During our visit, we saw a fox, a hare, a hawk, a woodpecker, and various interesting butterflies. In several places, the staff established picnic sites where you can legally stop, get the grill and dine in the national park. Most important, all of these places are located on the high banks of the Desna and offer great views.
The park has several ecotrails, one of them, "Rykhlivska Dacha", is well documented on the official website (but only in Ukrainian, use Google Translate). It's about 5 km long, the start and the finish points are in the Rykhli village. I sketched out a rough plan of this ecotrail.

The ecotrails are marked with signs. If the color has changed, it means that the paint was over =) ©Yuriy Buriak
There is also a 50-km driving route, it is described here.
We visited the local museum (information is here), it's located in two places and has been reconstructed in recent years. I wonder how it's possible that some things are aged 70 million years!
More photos from the Mezyn National Nature Park
Map of the Mezyn National Nature Park
Here you can find information about houses for tourists, where you can stay.
Getting there: Central Estate (museum) of the Mezyn National Nature Park is located in the Sverdlovka village. From Chernihiv go by minibus to Korop and then by minibus from Korop to Sverdlovka. Or by minibus "Chernihiv - Novgorod-Siverskyi" until the turn to the Pokoshychi village and then 12 km on foot or by hitch-hiking to Sverdlovka.