Feng Shui theory requires a curved shape.
The Jue of distinguishing the shallow and deep points of the lower acupuncture points in "The Ancient Mirror Song of Geography" says:
This section also talks about the road of Feng Shui. When life is prosperous, it is auspicious to be surrounded by bays, and when it is declining, it is good. If it is hard and straight, it will be bad. If you get the water from the prosperous palace, and you get the road to the prosperous palace to help it, you will be blessed even more. As for the paths in the fields, you should also look carefully. If it is shot straight and dead, it is called an earth arrow, and you should avoid it. Wang Mei, otherwise she would inevitably suffer from vomiting blood and heartache.
This requires that there are winding roads in front of the tomb, and the straight roads are "earth arrows", which is very bad! Very unlucky.