THEY say that in Glasgow, you should always look up: chances are you will be rewarded by a stunning architectural gem.

It could be an elaborate Victorian facade, Brutalist concrete, the signature Art Nouveau style of Charles Rennie Mackintosh or a glimpse of medieval stonework.

That adage has taken on new meaning in recent years with a joyous procession of colourful and eye-catching murals popping up across the city. Glasgow has embraced street art to brighten up its streets, reducing the gloomy visual impact of vacant land and shuttered shops due to the economic downturn.

The first large-scale mural – The Swimmer beneath the Kingston Bridge – was commissioned in 2008. Over the past decade many more have followed suit on bare walls, barren spaces and neglected nooks to create a vibrant tapestry of artworks.

Glasgow City Council launched its mural trail in 2014 and the accompanying web-app has since been downloaded almost 50,000 times to date. Several companies, such as Walking Tours in Glasgow and Photo Walk Scotland, have begun offering dedicated guided street art tours.

It's an ever-changing landscape with new murals appearing all the time: artist James Klinge is currently working on what is envisaged to be a 12-strong series next to The Arches at Midland Street. The first – a self-portrait of Klinge – is already proving hugely popular.

It joins an impressive body of work that Klinge already has on show around the city, including a clutch of animal-themed murals: Tiger Style on Clyde Street, Glasgow Panda in Gordon Lane and the Charing Croc which lurks beneath an underpass at, you guessed it, Charing Cross.

Klinge has also painted a series of murals – three to date – as part of his Study of a Woman in Black project which adorn walls at the Saltmarket, St Andrews Street and Royal Exchange Square.

The 35-year-old artist reveals there is much meticulous planning and preparation before he heads to the sites with his spray paint cans in hand. "The majority of the work happens in my studio preparing the hand-cut stencils for each piece," says Klinge. "It is intricate work to capture the detail.

READ MORE: Street artist Smug talks about creating some of Glasgow's best-loved murals

"With Study of a Woman in Black at Royal Exchange Square that was about three weeks' preparation cutting stencils in my studio and then three days to paint on site. The stencils do take a long time.

"The new mural at The Arches has gone up pretty quickly and people are amazed how quickly it has gone up, but it has taken me a month to cut the stencils. Figurative work is primarily what I do, and this job has allowed me to continue bringing my figurative work onto the streets of Glasgow."

There are around 25 locations on the mural trail. At Strathclyde University on the corner of North Portland Street and George Street, a clutch of giant artworks pay tribute to alumni and their achievements.

Featured are research pioneers and technological innovators such as John Logie Baird, inventor of the world's first working television, and Andrew Ure, whose experiments on corpses are thought to have inspired Mary Shelley's novel Frankenstein.

There is a towering mural of a telescope with a satellite hovering among the stars above. Another striking piece tells the story of the "Land-Ship", a mock navigation bridge that was used to teach students about the principles of compass adjustment.

Just around the corner on High Street is one of the city's most popular murals. Painted by the Glasgow-based Australian artist Smug – real name Sam Bates – it shows a bearded man gazing tenderly at a robin perched on his finger.

It depicts a modern-day version of Glasgow's patron saint, St Mungo, and references the story of The Bird that Never Flew on the city's coat of arms. Within a week of the mural being unveiled in 2016, its image was shared 1.5 million times on social media.

Last August, Smug created a beautiful companion work, a contemporary interpretation of the city's founding story showing St Thenue/Enoch cradling her baby son St Kentigern/Mungo. It bookends St Mungo on the opposite gable-end of the same High Street tenement.

Another of Glasgow's famous sons was honoured in 2017 when a trio of 50ft-high murals paying tribute to comedian Billy Connolly went on show, marking his 75th birthday. Based on original portraits by John Byrne, Jack Vettriano and Rachel Maclean, they were recreated on walls at Dixon Street, Osbourne Street and Gallowgate by Rogue-one and the Art Pistol collective.

Rogue-one – real name Bobby McNamara – is also behind The World's Most Economical Taxi on Mitchell Street, which shows a man hailing a balloon-powered floating cab, and Crazy Cat Lady, the purrfect felines painted on wooden hoardings along Sauchiehall Street where the fire-ravaged, now demolished, Victoria's nightclub once stood.

READ MORE: Street artist Smug talks about creating some of Glasgow's best-loved murals

Smug painted The Swimmer under the Kingston Bridge, celebrating the city hosting the 2014 Commonwealth Games, and brightened up Ingram Street car park with Fellow Glasgow Residents, a woodland-themed mural featuring badgers, foxes, squirrels, hedgehogs and deer.

Another by his hand is Honey … I Shrunk The Kids on Mitchell Street, showing a woman with a magnifying glass studying an unseen object on the ground, while the boarded-up exterior of a former shop on Argyle Street is revitalised as The Gallery, Smug's interpretation of famous paintings.

His canny homage to Leonardo da Vinci's Mona Lisa – a woman holding a can of Irn-Bru against a backdrop of the Clyde Auditorium and Finnieston Crane – has been dubbed "The Mona Lassie".

Street art by its nature is not permanent. Someone will tag it with graffiti – as happened to Klinge's panda mural – or it can disappear altogether as in the case of Rogue-one's Hip Hop Marionettes when the building it adorned on John Street was demolished.

While some may decry the transient nature of these installations, it is arguably something which could be viewed as a positive, reflecting the changing landscape as the city continually evolves and reinvents itself.

"One of the best parts is exploring bits of the city that you haven't been to for ages," says Klinge. "If there is a mural beside empty shop units, people doing the tour builds up passing trade and brings footfall to areas that there may not be regularly."

Klinge, who has been liaising with Glasgow City Council, The Arches and Network Rail on his latest project, has grant funding for three portraits at the Midland Street site. His aim is to complete 12 in total over the next two years.

"The first one is a male portrait," he says. "It is actually a self-portrait. I've had people look, then do a double take and ask: 'Wait, a minute. Is that you?' Some of the portraits in the series will be of DJs at The Arches during its history as well as other people who frequented it.

READ MORE: Street artist Smug talks about creating some of Glasgow's best-loved murals

"I have been preparing for this job since the start of the year. Once I got the green light, I started getting my photographs of the subjects, then got in the studio and started cutting the stencils."

Each portrait measures 4m (13ft) high and 3m (10ft) wide with Klinge using spray paint and multi-layered stencils. It is expected that all three murals will be completed by this weekend.

"My work has a dark aesthetic but the only stipulation for this job was to bring a bit of colour," he says. "Each figure is sitting within a circle of colour and within that each colour for each figure will be different."

Klinge, originally from Ayrshire but now based in Glasgow, works primarily in a studio and on canvas. How did he first fall in love contemporary street art and graffiti?

"I knew from a very early age that art was a career path I was going to pursue. Going into Glasgow on the train I would see graffiti along the side of the tracks and found that interesting to look at. Growing up I was inspired by hip hop culture, graffiti, rap, breakdancing and DJing.

"I have never done graffiti. I am not a graffiti artist. I'm not even a street artist – I am just an artist. Street art, for me, is simply working to a much larger scale than I do in the studio.

"Because I use spray paint that does see me being pigeonholed as a 'graffiti' or 'street artist', but even my canvas work uses spray paint. I work with stencils then I attack the canvas with a palette knife and move the paint around."

It's not all glamour as Klinge can testify. Among his biggest foes: battling the elements. "Working with stencils when it gets windy or rainy is a nightmare," he says. "There's been a couple of times I've been rained off. You wake up in the morning, look out the window and hope for the best."

Yet, these are merely minor grumbles. "It is exciting," says Klinge. "Even from when I was emulsioning the wall beforehand, I had people coming up and asking: 'Are you going to be doing a mural?' When I said yes, they would get excited. The murals are making so many people happy.

READ MORE: Street artist Smug talks about creating some of Glasgow's best-loved murals

"I think it is amazing that Glasgow City Council is investing to brighten up the city with these murals. From locals to tourists, it just brings smiles to people's faces. Some come back day after day to see how I'm getting on. There is a wonderful sense of pride that I get to do this for a living."

For more information, visit citycentremuraltrail.co.uk