Charts, globes, atlases and street plans are becoming ever more collectable as paper maps are slowly replaced by smartphones and satellite navigation.
Investors may be tempted down this route as a result, aware that they could lead to financial gain but, as with all investments, there is a chance of a fall in value.
Jessie Fahy is the manager of the Map House, which has one of the world's largest catalogues.
Last year alone, the store sold 20% more pieces than the year before.
Right now, they have everything from postcard-sized plans for a few hundred pounds, up to a Bleau world map dated 1665 which is worth around £1.25m.
"Over the last 20 years the map market has changed," she says.
"The number of people who are interested in it has increased. There is also a broader range of people coming in."
She highlights the street plans of London produced by Charles Booth. From 1889, his charts were released as books.
They were labelled with socio-economic information - such as the wealth or class of the people who lived on a particular road.
Thirty years ago such maps were mostly of interest to academics. Now, they are widely collectable.
Ms Fahy is selling a table-sized Booth map for just under £30,000. She says that price is around double what it would have been a decade ago.
The interest in maps seems to be coming from a younger demographic, unlike the usual customers for items such as antiques or books.
The biggest age group visiting the Map House's website is 25- to 34-year-olds.
"Maps are more prevalent now than they ever have been with access to amazing mapping on a smartphone," says Charlie Savile, a map expert.
"I think that's created a renewed interest in the process of mapping historically."
Not all maps have risen sharply in value, according to map seller Tim Bryars.
Historic regional charts, particularly those of smaller towns and rural provinces in France, have not risen much more than general inflation.
Areas that have caught the eye of collectors are those with a geographic or historic relevance for a large number of people, particularly places where incomes have risen sharply.
That has boosted the price of plans of the world's major cities, like London, Hong Kong and New York.
It has also lifted the value of maps in countries such as India and China.
"There is a growing Indian middle class," Mr Bryars says.
"And people there have also seen their wealth rise. They have a great interest in their history."
But you do not have to invest large sums, if you get lucky.
Plans of the London Underground network have become strongly collectable.
Ten years ago, the January 1933 Tube map that was originally given away free in stations, would have cost between £300 and £500.
Now the map is sold for more than £1,500 a copy.
Like Mr Savile, Mr Bryars believes the internet is behind these rising prices.
"A few years ago I do not think people realised how rare some of these items were," he says.
"The assumption was that something that was three or four hundred years old was automatically worth more."
"Now it is much easier to see there are pieces of 20th Century ephemera, often which were given away for free, that we can now put into their proper historic context.
"Because of the internet we have a better understanding of their rarity."
So if you have an old A-Z kicking around or a subway map left over from a trip to New York stuck in a drawer, you may want to hang on to it. It could be worth more than you think.