Citymapper has raised £32 million for its urban navigation app

Citymapper, the urban navigation app founded by a former Googler, has raised $40 million (£28.2 million), bringing total investment in the company to $50 million (£35 million) and giving it a valuation that's likely to be in excess of £250 million.

The Series B round, which comes 21 months after a $10 million (£7 million) Series A round, involved Index Ventures and Benchmark Capital, as well as individuals including Yuri Milner, Tom Stafford, and Michael Lynton. It was first hinted at by Sky News on Monday.

Instead of the standard press release, the London-based startup announced the funding round in a quirky Medium post where it joked that its investors had promised to "only take buses from now on." In the 11-point post, Citymapper said it will use the funding to refine the Citymapper app, help it expand into more cities, build out its team, and launch new products. It also said that it's developing Citymapper's API/Widgets so that other app developers can use them to power their own websites and applications.

Founded in 2011 by Pakistani-born ex-Googler Azmat Yusuf, Citymapper began life as an app exclusively for Londoners. The app has since expanded to cover over 30 cities - including Madrid, Sao Paulo and San Francisco - but Yusuf doesn't plan to stop there.

"It's not just about London, NYC and Paris anymore. The next set of challenges involve the massive emerging market cities where the infrastructure is limited, rules of transit are different, data is sparse, and even the consumer approach to smartphones and apps is not the same," the Medium post reads. "But this is also where some of our most rewarding work is being done."

The company added that it's going on a huge recruitment spree, stating that it wants to hire people in "every significant metro city in the world."

Citymapper's algorithm pulls in vast amounts of data to present users with a range of transport options, including bus, train, metro and Uber. The results are presents through a sleek-looking green app that also displays information such as journey times and prices.

Londoners and other urban dwellers have embraced Citymapper for its simplicity and its comedy value. The app, for instance, shows users how long it would take them to get from A to B using a jetpack or how many doughnuts they would burn off if they walked instead of taking the bus.

Citymapper has been quiet with regards to user numbers but the app often features towards the top of the transportation app download charts for both iOS and Android.

Balderton Capital, one of Citymapper's former investors, was absent from the latest funding round. Bernard Liautaud, general partner at Balderton said: "Citymapper is an exceptional company with great potential, and we're thrilled with the progress the business has made. We are proud to have led the previous round in 2014, and remain active, engaged investors."

Citymapper finished its blog post saying it's not a unicorn, which is the term given to a company worth over a billion dollars. It added: "We're more like a dolphin??."