A cycling and walking tunnel between two valleys in south Wales will be the longest in Europe when completed, and will have a host of features to make the journey more fun.

At 3.1km (1.9 miles), the Rhondda tunnel, built for rail, will also be the longest in the world for six months of the year, during which a tunnel in Washington State, USA, closes for the winter.

The tunnel, which connects the Rhondda and Afan valleys, fell out of use in 1970 after 80 years of service on the Rhondda and Swansea Bay railway line, and the cuttings at each end were filled in. But a project, which has been more than 10 years in the making, aims to reopen it for cyclists and walkers.

It took a significant step forward last week when the local Rhondda Taf Council approved plans to excavate the Blaencwm end of the tunnel in the Rhondda Valley, exposing it for the first time in nearly half a century.

The Rhondda Tunnel Society, who are spearheading the project, hope to complete the reopening in stages, with the next one being to excavate the Blaengwnfi end in the neighbouring Afan Valley, before beginning work on making it cyclist-ready.

Tony Moon, RTS project manager, gave Cycling Weekly an idea of what the experience will be like.

"There will be lighting all the way through, and unlike other tunnels, like the Bath tunnels, we feel we need mobile phone access now, so there will be at least emergency phone access through the tunnel," he said.

The current route between valleys is on good roads, but involves a lengthy climb, according to Moon, a bike rider himself. The reopened tunnel is likely to appeal far more to anyone feeling less energetic. Moon also raises the possibility of holding a cycling event that climbs over the hill and comes back through the tunnel.

"It would make a lovely run – or the other way around. I'm quite sure that big cycling events will happen as a result," he said.

The long underground trip is likely to take up to 10 minutes for bike riders and 40 minutes for walkers, and to help it pass more quickly users will be kept entertained along the way.

"[There will be] audio-visual displays at different parts of the tunnel," Moon says. "One long section has some very good alcoves in it, so what we'd like to do there is use the alcoves as exhibition space, put all sorts of different features in there."

Local schoolchildren have already been recruited, he says, to help design an exhibit.

Work to complete the tunnel will take around 18 months, Moon told CW, though added to that would be time spent fund-raising for each stage.

Martin Roberts, TV presenter and RTS patron, said: “The re-opening of the tunnel as a walking and cycling route will have massive impact on the area, from an economic, social and tourism perspective… and will be pivotal to enhanced cycling, walking and active travel in the region.”

Whichever side of the north/south divide you favour, Wales offers a network of incredible riding terrain that's just begging to be explored.

From craggy Welsh mountains to coastline rollercoaster roads, the roads vary as dramatically as the accents, and if your ride happens to cross the border then you'll have the pleasure of saying you've ridden two countries in one day, too.

We've pulled together some must-ride locations, from individual climbs to full routes for you to try...

>>> Vale of Glamorgan with Nicole Cooke

Horseshoe Pass from Wrexham, North Wales

https://www.youtube.com/watch?v=xthtag22JHc&t=178s

A personal favourite, the Horseshoe Pass (or 'Bwlch yr Oernant' if you trust your pronunciation) is conveniently located around a half hour ride from the house my other-half grew up in, so a ride to the ~20-minute ascent has become an annual Christmas family tradition (provided it's not snowing, raining, hailing, or sleeting).

The climb begins as you exit the absolutely stunning town of Llangollen, which is sliced in half by the River Dee and offer the perfect stop for a quick pre-climb coffee.

The ascent itself is 6.2km long and averages 5 per cent, with the steepest gradient at 12.2 per cent (ignore the 20 per cent sign on the hairpin.

On Strava, the best women's time was set by Bethan Jones, with 17.59, whilst the men's KOM belongs to Giles Drake with 13.20.

The stretch, named after  the u-bend midway, is frequently used in the hill climb season, and was the venue for the National Hill Climb in 1976 and 1981. The descent which follows is flowing and not technical - and there's plenty more climbing to be found in the area if you're looking to go on.

Dragon Ride from Port Talbot, South Wales

Typically held in June, the Dragon Ride is a well established sportive that's typically over-subscribed thanks to its legendary status.

It's worth bookmarking the page if you want to ride in 2020 - but if you'd just like to explore the route, you can download a GPX file and head to the start in Port Talbot any time you like.

>>> Cycling Weekly takes on the Dragon Ride

The long route (297km) comprises of almost 5,000 metres of climbing - including The Bwlch, Devil's Elbow, Bwlch Bryn-Rhudd, Devil's Staircase and Black Mountain. They're as tough as the names suggest.

Wye Tour from Monmouthshire, South Wales

The Wye Valley Area of Outstanding Natural Beauty straddles the border between England and Wales, and is named after the fifth longest river in the UK - which slices through it.

There's the opportunity to explore the area on the Wye Tour Sportive, hosted by Cycling Weekly's sister company, UK Cycling Events, on Saturday August 31.

>>> Sign up: Wye Tour Sportive, August 31

The route crosses the River Wye itself, following the eastern bank. Those on the longer 152km route will head towards the Forest of Dean, before descending into Lydney, overlooking the Severn Estuary. Riders then trace the Dean Forest Railway, ahead of some unmissable panoramic views at Cinderford, before a thrilling descent into Upper Lydbrook.

>>> South Wales with Magnus Backstedt

The final sting in the tail will be Star Hill, but this offers some beautiful glimpses of the Brecon Beacons before the return journey to Chepstow.

>>> Black Mountains with Cycling Weekly 

This particular route covers over 2,000m of climbing - so it's no walk in the park, but the views make each pedal stroke more than worthwhile.

Ffordd Pen Llech in Harlech, Gwynedd, North Wales

Unless you studied Welsh at school, it's probably a bad idea that you try to pronounce any of the place names above. What you do need to know is that the gradient on this hill tops out at a jaw dropping 37.45 per cent.

This is a stretch well known to Cycling Weekly editor Simon Richardson, who took part in the recent hill climb held on the newly crowned 'steepest climb in the world'.

The fastest female and male times on the Strava segment are 2-11 from Sally Minchella and 1-23 from Nicholas Gevaert.

Whilst it's just over 300 metres long, it's probably a good idea that you take a spin around the area to warm up.

Cambrian Mountains, Mid Wales

The Cambrian Mountains form the backbone of Wales, and the area is known for carrying an air of wilderness, largely thanks to the sparse population and far reaching moorlands.

>>> Trans-Cambrian Sportive with Cycling Weekly

The highest point is Pumlumon Fawr, at 2468ft-or 752m - far from the realms of altitude sickness, but high enough to throw up some pretty meaty climbs.

When Cycling Weekly visited the area, we were guided on the best roads by the route of the Trans Cambrian Sportive, which took in "some of the finest mountain scenery in the UK... there are high moors, deep verdant valleys, flat grey lakes, and steep dappled forests."

>>> Mid-Wales with Yanto Barker

The route began in the market town of Rhayader, dropping into Llanidloes before heading west over the Cambrians. An eight-mile downhill to Machynlleth followed, before we headed along the coast to Aberystwyth. From there, we took on the five-mile climb to the Nant y Moch reservoir; then south again to the head of the gorgeous Elan Valley, and finally south-east homewards and back to Rhayader.