To calculate the circumference of a circle, you can use the formula:
\[ C = \pi \times d \]
where \(C\) is the circumference and \(d\) is the diameter. Given that the diameter is 8 kilometers and using \(\pi \approx 3.14\), we can substitute the values into the formula:
\[ C = 3.14 \times 8 \]
Calculating that:
\[ C = 25.12 \text{ kilometers} \]
So, the estimated circumference of the circle is 25.12 kilometers.