There are 81 official mountain bothies in Scotland and Geoff Allan has stayed the night in every one of them.

From the northern reaches of Sutherland to the wilds of Argyll, Geoff has spent the last five years criss-crossing the country by bicycle in an effort to document every outpost maintained by Scotland's Mountain Bothy Association.

But as he raised a glass of champagne after reaching his 81st bothy - a small stone cottage nestled within Dumfriesshire's Eskdalemuir Forest - Geoff couldn't bring himself to end his one-man odyssey.

Using only a bike, some supplies and a set of coordinates, he has now embarked on a new quest to uncover another 81 of the unofficial hideaways dotted throughout the country.

While the exact number of bothies remains a bit of a mystery, Geoff has explored Scotland's rugged landscape more than most and estimates there is around 180 that are in a habitable state.

"They are not hard to find, once you've got the grid reference," he says.

"They are just hard to find out about. I'm just going to start ticking them off where I can."

Fascinated by the bothy tradition since moving to Edinburgh in his 20s, the freelance artist and photographer saw bothies as the perfect way to enjoy Scotland's scenery on a budget.

And once he set himself the challenge, he started his Bothie on a Bike blog and the trips became the focus of his free time.

"It has been a life raft for me because I have not settled down," Geoff says.

"I would go away to the hills to escape but then there became a reason to go away."

Bothying dates back to the end of the Second World War when hillwalking grew in popularity, creating a use for these small, abandoned cottages once occupied by estate workers.

In 1965, Yorkshireman Bernard Heath founded the MBA to help maintain these shelters, which have been funded solely by the donations of volunteers ever since.

With around 4000 current members, MBA trustee Neil Stewart says numbers have been gradually increasing in the last couple of years.

"There are still old buildings around that we are asked to consider," Neil says. "We add a new bothy to our list most years."

For Geoff, it is the challenge of navigating a route to the bothy and then surviving without any running water or electricity that he enjoys most.

Most are very basic inside with usually only a table, a couple of chairs and a fireplace or a stove inside.

"You have to be self-sufficient but if you put a bit of effort in, you can make it homely," says the 46-year-old.

"They can be cold, dusty and damp and, in the winter, pretty dark.

"Fire is absolutely essential. I will walk a mile to get firewood. You need fuel and a good sleeping bag."

From battling up Cairn o' Mount's unforgiving slopes to discovering isolated little cafes, each bothy brings with it a new experience.

"In the winter, the light is great because it holds a certain colour," Geoff says.

"The amount of times I have woken up in the morning and the view is just stunning. That's one of the reasons I go.

"There's a bothy in Sourlies, which is the head of Loch Nevis. It's an eight-mile walk whichever way you come from and at the head of a loch. The bothy itself is not brilliant but the location is.

"I went away one Christmas and went up a hill and saw atmospheric thing called Brocken Spectre, an angle through the mist where you get a shadow of yourself with a rainbow around it."

The companionship found in these little homes is also a big part of the experience.

"I once woke up on a Sunday morning and I needed to get to a bothy in the Borders," he says. "I rolled out of bed and decided to just go.

"It was over two sets of hills, a 50-mile cycle up and down.

"I walked toward it and there was a light in the window. It was Sunday night and I was exhausted. I walked in and there was a band with two guitars and a bass and we had a sing-along.

"I sat there, a generation older than everyone else and they got me a seat by the fire.

"I thought, 'Bring it on'. I didn't even know what a Jagerbomb was but I sat by the fire with my red wine and we just sang all evening."

With a book in progress and a new challenge under way, Geoff has changed the tagline of his blog to an "ongoing odyssey to document every bothy in Scotland".

To date, he has ticked off around 25 on his new list, with bothies in the Shiant Isles, Mingulay and Scarba on the horizon.

"No two bothies are the same, and each has its own unique charm and character, but ultimately it's how you make yourself at home that makes the difference to your bothy experience," Geoff adds.

1. Staoineag bothy - near Loch Treig

"I've stayed in this bothy the most, nine times in all.

"The easiest way to get there is by train so you don't need a car."

2. An Cladach bothy - Islay

"This is a home from home if you get it to yourself. A single room right by the shore with a view down the Sound of Jura."

3. Kearvaig bothy - Sutherland

"Not only has it been renovated recently and has the feel of a hostel. But the setting - in its own bay close to Cape Wrath - is amazing."

The most luxurious: Cruib bothy - Jura

"The main room in Cruib on Jura has a library and carpet, a sleeping platform and writing table.

"Just like a hostel room, it's actually warm in the morning after the fire the night before. As it's so difficult to get to, you generally have it to yourself."

The most isolated: Maol Bhuidhe - Islay

"Maol Bhuidhe is the most isolated bothy. There are a couple that are similar sort of distances but when your out there you really feel in the middle of nowhere."

The best view: Rubha Hunish - Skye

"The best view is from the Lookout at Rubha Hunish on the north coast of Skye. Not a great bothy - no stove or water - but it has a wow factor."

Find your nearest mountain bothy in the link below.