The old railway line connecting Wellington and Wairarapa with 4 tunnels, 2km single track, 6km double track and 15km of unsealed gentle slope on the Hutt Valley side. You can either cross from one side to the other or just ride to the summit and return.
There are several circular forest tracks on the Wellington side of the summit for an interesting diversion. Take a torch for the tunnels as the longest tunnels and those that bend can be pitch black. Best to ride the tunnels slowly rather than walk them as there is often water under foot. You may have to carry your bike the short distance through Siberia Gully depending on recent washouts. Please control your speed when descending on the eastern, Wairarapa side.
The Rimutaka Rail Trail was once a rail route established in 1878 between the Hutt Valley and Featherston that carried passengers up the steep incline from Cross Creek to Rimutaka Summit until the opening of the Rimutaka rail tunnel in 1955. The innovative Fell mountain railway system pulled trains up the steep slope of the Rimutaka Incline.
DOC and the Wellington Regional Council now jointly manage the incline as the Rimutaka Rail Trail. DOC manages the Incline section from the Summit to Cross Creek carpark in the Rimutaka Forest Park, and Greater Wellington Regional Council manages the section from Kaitoke to the Summit in the Pakuratahi Forest.
This track follows the famous Rimutaka Incline railway line. From part way through the Summit Tunnel down to the rail yards the slope is typically 1 in 15 - a modest gradient for a mountain bike, but extremely steep for a railway line.
Along the way there are three tunnels to pass through (in order, from the top): Summit Tunnel (576m long), Siberia Tunnel (108m long), and Prices Tunnel (98m long). It is advisable to take a light of some form for the Summit Tunnel. Although the Summit Tunnel is straight - so the other end is always visible. The other tunnels are curved but are sufficiently short that they don't really require a light.
About 400m down hill from the Summit Tunnel there is a lookout that provides sweeping views of the valley.
Just below the Siberia Tunnel is Horseshoe Gully - otherwise known as "Siberia" due to the local micro-climate. There was a curved earth embankment across the gully until, in 1967, it was washed away. Now there is a deep gully that has signs stating "Steep, slippery approach to creek bed. Cyclists are advised to dismount and walk". Chances are you'll have to dismount to cross the creek and ascend the other side anyway. Note that the track on the summit side of the gully is about 25m upstream of the track on the Cross Creek side.
As would be expected from an old railway line, the track itself is fairly smooth and evenly graded with gentle curves. Nonetheless, watch out for the occasional rut and stone on the track - especially if descending at speed.
The bottom of the track is at the old rail yards that formed the Cross Creek Station and settlement. From there, either return back up the incline or continue along the Cross Creek track.