Bolu will be a whole new city if you decide to see it on four wheels by renting a car since you will be able to go where you wouldn't be able to otherwise. And, by the way, there are much more than just a few car hire offices in the city, with pick up locations at Downtown. To avoid any inconveniences, ask the hotel personnel for advice on where to park near the main sights and which rules should certainly not be broken on Bolu’s roads.