Two people in their 40s are being treated in hospital after being found lying on a pavement in Kinver suffering serious head injuries.
Emergency services were called to the Staffordshire village shortly after 1am today after a passer-by spotted the man on the ground in Enville Road.
He was taken to the Queen Elizabeth Hospital in Birmingham and was today described as being in a "serious" condition.
Patrol officers also found a woman a short distance away, also with head injuries. She was taken to Russell's Hall Hospital in Dudley.
Police have appealed for anyone with information about how the pair were injured to get in touch.
They're cold, they're damp and they haven't been used for more than 20 years but a network of underground tunnels could become a Midlands tourist attraction.
The owners want to open a visitor centre and build houses to finance their plans, which would see people allowed into a previously secret world for the first time.