Uber has announced an enormous new round of funding this afternoon. The company is taking on $1.2 billion in fresh capital, an investment that values it at $17 billion, not counting all the cash it has in the bank. The only startup to raise money at a higher valuation before going public was Facebook.

Uber was launched four years ago in San Francisco. It now operates in 128 cities in 37 countries around the world. It has plans to expand beyond offering taxi and black car rides to several areas of transportation and logistics, from family carpools to delivering air conditioners.

While the enormous valuation associated with the round has already raised questions of a tech bubble, the blue chip investor profile implies the company has solid financial fundamentals to back up the hype. The new funding comes mostly from mutual funds — Fidelity Investments, Wellington Management, and Blackrock — with four of the venture-capital firms that previously backed the company also joining this round. "The common gut reaction when you see a number like this is that it's irrational," says Bill Gurley, a venture capitalist with Benchmark who currently sits on Uber's board. "But this is the fastest-growing company we've ever worked with, comparable to the early days of eBay."

Leaked documents obtained earlier this year by ValleyWag showed that Uber was on track to process over $1 billion in rides for 2013, of which it keeps around 20 percent, or $200 million, in revenues.

Uber's biggest rival, Lyft, raised $250 million back in April, a move that put its cash pile on par with Uber. It's unclear if Lyft plans to raise again now that Uber has acquired this massive war chest, but it has certainly fallen far behind in the battle of the best-funded taxi apps.