Riding alongside the roaring Ōhinemuri River through the Karangahake Gorge it's hard to believe the place was once declared a sludge channel, where gold miners were free to dump toxic tailings.
The river became clogged with cyanide-laden silt and dead fish and eels floated to the surface. It was known as one of the most abused rivers in the country.
But gold rushes don't last forever. The river has largely recovered and now it can shift boulders the size of buses, plus the trout fishing is good.
What's more, the gold rush that started in 1875 has left a fascinating historic legacy and one of the easiest Great Rides of New Zealand.
The old rail line is well gone and its level path carved, smashed and blasted through the rugged gorge is a wide and well-kept Grade 1 trail within easy day trip range from the big cities of the upper North Island.
At the peak of mining, about 3000 workers made a tough and dangerous living in the middle of the gorge.
On the trail you see the remnants of mighty stamping batteries that crushed quartz ore to dust before it was processed with cyanide and you pass through a 1.1km rail tunnel critical for the mining industry.
You can start the ride in Waihi but I set off part-way through the gorge at the Waikino Station Cafe. It's a fine place for a cuppa and you'll find terrific photos from the gold rush days and plenty of information about the Hauraki Rail Trail, which now can take you on three directions.
On an earlier ride with a friend, we went to Thames but this was a solo cycling journey so I opted for the shorter trail to Te Aroha, 35km in total.
You could knock off a 70km return journey in a day but it helps to have someone to drop you off. While I was cycling, my wife was able to have a cruisey half-day from Auckland, taking a walk in the gorge and exploring the second-hand stores and cafes in Paeroa (The Refinery in Willoughby St is a good spot) before the rendezvous in Te Aroha.
The trail is billed as being suitable for riders of all abilities, which is right but make sure your bike's in reasonable knick. I used one with narrower commuter tyres on my first ride a couple of years back and suffered two punctures in a worn tyre. You could get away with it, but a mountain bike with knobbly tyres is still the way to go.
Lights, or a torch for the long rail tunnel are a good idea to help see and more importantly, be seen. The Karangahake section is the best bit so take your time looking around the mining relics, enjoy the bush and if you feel like a bracing dip, the river is great for cooling off.
It may be a good time to do it because the miners are back in the gorge. New Talisman Gold Mines bosses, in the way of explorers, are bullish about what they can still squeeze from Mt Karangahake but environmental activists are determined to stop them.
Once out of the gorge you're soon into farmland and when heading for Te Aroha you turn left at a junction where signs for cyclists aren't exactly in your face.
The trail is straight and being part of the old rail formation is flat but, into a reasonably stiff southerly, a bit of a slog.
I was reminded, as I ground towards Te Aroha, that I like my riding with a bit more topography and a few more turns. The farming was a little monotonous too and a reminder of the industrial scale of the dairy sector. It's a muddy, dung-splattered business and there's a regular whiff of silage.
When you're riding through similar country from Paeroa to Thames, there are more options to stop, including The Cheese Barn, outside of Kōpū. And it's easy to co-ordinate meeting up with your support crew in cars along the way. Fish and chips on the wharf when you get to Thames is a great way to finish that section of the trail.
Still, the Te Aroha ride clears the sinuses and the wide-open plains a great contrast to the city if you're living in one.
If you're keen for some more demanding riding there's a 7km mountain bike trail on the foot of the mountain near Te Aroha's domain that is suitable for a range of skills.
And at the end of it all, if you have time, the mineral spa is great for a soak.
Hauraki Rail Trail
The 136km trail showcases some of the region's best scenery, and as a Grade 1 cycle trail, it is suitable for all fitness levels and cycling skills. Accessible from Kaiaua, Thames, Paeroa, Te Aroha, Waihi, Waikino and the Karangahake Gorge.
It can can be ridden in comfortable day sections, or as a multi-day journey. With section five currently under construction, the leg from Te Aroha to Matamata will see the trail increase to 173km in length.