Special Containment Procedures: The entrance to SCP-XXX is to be guarded by no less than four armed Foundation personnel, and is to be disguised as a checkpoint to prevent unauthorised access. The railway lines leading into SCP-XXX has been decommissioned and monitored as to prevent trains from entering the anomaly.
Description: SCP-XXX is a spatial anomaly located in ████ ██████. Currently, the SCP can only be entered from the south of the 'entrance' (A stretch of road crossing over the railway tracks). Attempting to enter from any other direction yields no anomalous results.
The anomaly consists of a single railway line that extends north arbitrarily far. Both sides of the track have an apparently limitless field of grass with sporadic shrubbery. No animals have been observed in the SCP. See Incident Report XXX-I3
Personnel sent in with GPS equipment report the co-ordinates not changing from the entrance of the anomaly, despite distance travelled. Radio-transmitting equipment does not suffer any loss of signal, even when the distance travelled is well outside its operational limits. Video and picture transmitting and recording devices cease to work once within 50m into the anomaly, showing a frozen frame until back within 50m of the entrance.
Personnel exploring SCP-XXX describe the right (east) side of the railway line suffering distortion, becoming more severe the deeper they go in, occasionally breaking the laws of physics (personnel describes the land circling up and looping back on itself, yet remaining flat at the same time). Approximately 100m in, the subject exploring the SCP suffers a loss in colour perception, describing their vision as complete grey-scale once 1000m in. Returning to the entrance restores perception of colour at the same rate.
The west side of the tracks do not suffer any distortion or anomalous affects (beyond that of extending Northwards infinitely).
After 1000m into the anomaly, subjects report that an unknown entity is following them. They have never been able to directly perceive or see the entity, saying it is always 'in the corner of their eye'. Entity is presumed benign, as no personnel has been harmed by it. See Incident Report SCP-XXX-I1
After the loss of Agent ██████ during Incident SCP-XXX-I1, only D-Class Personnel are permitted to enter SCP-XXX.
The furthest distance travelled in SCP-XXX is 21.6km (as measured by surveyor's wheel). See Incident Report SCP-XXX-I4