Tapui Railway Tunnel 

Exploring Tapui Railway Tunnel (On private land / Partly flooded.)
(The Ngapara and Tokarahi Branches were two connected railway branch lines in northern Otago, New Zealand, part of the national rail network. The Ngapara Branch opened in 1877 and almost all of it closed in 1959; the remaining few kilometres, called the Waiareka Industrial Line, were removed in 1997. The Tokarahi Branch branched off the Ngapara Branch. It operated from 1887 until 1930 and was originally known as the Livingstone Branch, though it never progressed beyond Tokarahi to Livingstone.
In the early days, motive power included the FA class, which were stationed in Ngapara and were known to haul the passenger train from Windsor Junction to Oamaru prior to 1918. Other classes utilised included the P, T, UB, UC, WD, and WF. T class are known to have operated to Tokarahi into the 1920s.
Alps to Ocean Cycle Trail.
The final section of the Alps to Ocean cycle trail (from Duntroon to Oamaru) follows these two branchlines in places.
The cycle trail follows beside the Karara Creek and intersects the Tokarahi - Windsor line at a point approx 4km from Tokarahi, and 1km from the Tokarahi-Ngapara Road. Trail, creek and railway formation run roughly parallel for a kilometre before creek and trail diverge, although the formation can be observed for most of the next kilometre. Approximately 5km further the trail drops down Tunnel Road to the western portal of the Rakis Tunnel and follows (mostly on) the formation for six or seven kilometres to a point about 1.5km short of the junction at Windsor.
After leaving Enfield. (on the Ngapara Branchline) the cycle trail follows on the railway embankment for about 1km (including a significant bridge) until rejoining the Weston-Ngapara Road. The trail again follows on the railway formation from east of the lime works at McCormacks, through Weston, to a point about 200m short of the former junction with the Main South Line at Waiareka.)