Nikšić is the second largest city in Montenegro. In Nikšić proper there are a few interesting sites to see but most of the really interesting places are located on the way to or from the city such as the Ostrog Monastery.
One hour by bus from Podgorica, 3 euro for one way, frequent busses. Scenic ride.
Veliki Ostrog monastery is one of the most popular religious touristic destinations in Montenegro. Located only 15 km south-east on the road to the capital Podgorica, this middle-age monastery is worth to be seen in area of Nikšić.