With 28,039 retail locations around the world, Starbucks (NASDAQ:SBUX) is hard to escape. The chain has locations in supermarkets, airports, national parks, and even tucked into the theme parks owned by both Walt Disney and Comcast's Universal Studios.

Still, despite the chain's ubiquity, not everything about its past, or even its present, is widely known. The chain that has made "Frappuccino" a household word still has a few secrets worth discovering.

 A collection of Starbucks mugs.

Starbucks even has secret sizes on its menu. Image source: Starbucks.

1. There is a secret menu, sort of

While the chain does not have an official secret menu, it does have a number of drinks that have become unofficially offered if you know how to ask for them. In some cases, local baristas even use the chain's blackboards to make some of these drinks specials.

The chain does not call the existence of these drinks a secret menu. Instead, it acknowledges that customers can ask baristas to make anything that's possible using the ingredients in the store.

"Starbucks does not have an official 'secret menu,' however our customers are always trying out new ways to customize their favorite drinks according to their personal taste preferences," a company spokesperson told The Motley Fool via email in 2016.

If you want to order off the secret menu, it's best to know the recipe for the drink. For example, if you want a Caramel Cocoa Cluster Frappuccino -- a drink that was actually moved from the secret to the real menu for a while -- ask for toffee nut syrup, Frappuccino Roast Coffee, milk and ice, topped with a layer of caramel sauce, finished with whipped cream and a drizzle of mocha sauce.

2. There's a Starbucks at Yosemite National Park

While it's easy to joke that Starbucks is everywhere, the chain actually does have a location inside California's Yosemite National Park. The store, which has no sign, is part of a remodeled Base Camp Eatery that exists where the park used to have a food court.

This is the first Starbucks in a national park. It was built to Leadership in Energy and Environmental Design (LEED) standards, which the coffee company called "the world's most widely used green building rating system," in a press release.

3. Howard Schultz is not the founder

While Schultz deserves the credit for making the chain into what it is, he did not found the company. That honor went to Gordon Bowker (a writer), Zev Siegl (a history teacher), and Jerry Baldwin (an English teacher), according to Thrilllist.com.

Schultz joined the company in 1982, before leaving for a brief period to start his own Il Giornale coffeehouses. He returned in 1987, buying the company with a group of investors and slowly turning it into his vision of a "third place" beyond work and home.

4. The menu has secret sizes

Starbucks has replaced small, medium, and large with the fancier sounding Tall, Grande, and Venti. Those, however, are not the only sizes offered.

The chain also will sell you a "Short," which is an 8-ounce serving, and a "Trenta," which comes in at 31 ounces, but can only be used for cold beverages. To get a Trenta, you will have to order in person, while "Short" shows up as an option for hot beverages in the chain's app.

5. Starbucks used to sell soda

For a successful chain, Starbucks has failed a lot. One of its biggest failures -- Fizzio Soda -- was supposed to be launched nationwide, but it only made it to a portion of the country. If you didn't live in a market that got the beverage line, which made it to 16 states, you may not know anything about the low-calorie store-made drinks.

The chain dropped the Fizzio line without any fanfare or public announcement. It did confirm the end of the sodas in an email to The Motley Fool.

"Regarding your question about Fizzio, as our carbonation offerings evolve, handcrafted sodas are no longer a part of our menu," wrote a company spokesperson. "We remain committed to the carbonation platform and look forward to bringing even more experiences to our customers soon."

6. There is a 10-minute rule

No, this is not related to how long an item can be used after being dropped on the floor or how long a drink can sit before its thrown away. Instead, the company expects locations to open their doors 10 minutes before the posted opening time and keep them open ten minutes after, according to John Moore, who was a corporate marketing manager at Starbucks in 2002 and now serves as a marketing strategist.

In general, Starbucks locations actually close when they have served the last customer in line before the doors close. That's not an official policy, but the chain teaches its staff to be customer-friendly, and turning people away does not meet those standards.

Daniel B. Kline has no position in any of the stocks mentioned. The Motley Fool owns shares of and recommends Starbucks. The Motley Fool has a disclosure policy.