Where does the earth rotate the slowest?

The Earth rotates at a constant rate of once every 24 hours all over, in terms of revolutions per day. But nearer the poles you will have a slower relative speed. Its like a wheel of a car. Every point on the wheel is making a revolution in the same time, but nearer the centre of the wheel there is less distance to cover in that time, so the relative speed is slower than at the wheels edge.