If you're looking for a meeting place or a good stop around ½ or halfway between Nesvizh and Narowlya, you can try Zhytkavichy, Belarus, which is about 2 hours southeast of Nesvizh, or about 2 hours west of Narowlya.
About ¾ or three fourths of the way, you can stop at Mazyr, Belarus. This is a little over 3 hours southeast of Nesvizh, or almost an hour west of Narowlya.
If you drive straight through without stopping at all, the total distance is 336 km. The distances shown above don't include local roads to get into each town, so if you're planning a long road trip, make sure you factor in traffic and road conditions, rest stop breaks, and interesting detours along the way. If you're in a rush, you can do the trip with zero stops, and your total travel time would be around 4 hours, 7 minutes.
