Everything you're ever told in a tour is wrong. Well, maybe not everything, but stories and ideas turn into facts, which telephone-game into new facts. For a historian who loves to tour historic sites, it's a deeply concerning notion.

If you've ever taken a guided tour of Grand Central Terminal in New York City, I humbly hope you will put aside what you've learned. It's been my single largest project to rewrite this Wikipedia entry – on one of the busiest train stations in the country – and find out the truth behind widely repeated myths. I teamed up with about a half-dozen other Wikipedians, historians, journalists, and photographers to find the truth and write out this immense project. It's there that we began myth-busting most of the modern works about Grand Central.

There's four bold statements, repeated in semi-official tours of the terminal (and especially for its centennial in 2013) that we'll cover in this article. Journalists attending the celebratory events that year are responsible for repeating these statements. They've stood out as so unbelievable that I felt they warranted looking into.

1. Grand Central has a four-sided clock in the center of its Main Concourse, made of the precious gem opal, and worth $10 to 20 million.
2. The front of the terminal has a massive clock, designed by Tiffany Studios, and the largest Tiffany clock in the world.
3. The terminal's secret sub-basement, holding an electrical substation that powers the terminal and its tracks, was a target of the Nazis during World War II, which they failed to sabotage.
4. The terminal's famous constellation ceiling is backwards, either on purpose "the way the Gods would see the stars" or by mistake "Oops the reference sketch was held at my feet, not at the ceiling".

I'm hoping to better establish a permanent record on these. Let's dive into the first tale. While some sources have identified it as opalescent glass, due to its opacity, news began spreading the myth of "pure opal" in 1999 and 2000 – and again in 2006. Wikipedia (!) picked up this tale in 2006, where it remained until 2013. In this time, Smithsonian Magazine, PBS, LA Times, CNET, Mass Transit Magazine, 6sqft, Time Out New York, and even Grand Central Terminal's official website picked up this idea as a fact. Bill Burns was the first one to act against this myth, emailing research to the news site Untapped Cities. He emailed me as well, and working with User:Epicgenius, we found enough reliable sources to dispel the myth, and found no mentions of "opal" prior to 1999; instead sources referred to the clockfaces as glass. The New York Transit Museum, which has one of the original clock faces (replaced after being shot out with a bullet or BB), confirmed that their clock face is made of opal glass. And so, using all of our research, Untapped Cities published "Is the Grand Central Clock Worth $20 Million?", finally disproving this rumor in a concrete way.

The second "fact" is easy to disprove, again simply with how it's been described over time. There is a massive glass-faced clock on the building's exterior, but it's not from Tiffany Studios. Sources from 1995 into the present day claim it, again including Grand Central Terminal's own website. But yet most of the sources that mention the clock, and all those from before 1995, do not mention Tiffany. Some go far into detail about the clock, and the notable glassmaker would have been mentioned.

As well, none of the five books about Louis Comfort Tiffany that I referenced mention the clock. I would love to examine the clock to better-ascertain its creator(s), but I was denied access to that space and all other non-public areas of the terminal. Anyhow, portions of the glass have been replaced during restorations. The restorer, Rohlf's Studio, found no signatures on the original glass pieces, and a 1913 list of contractors included Tiffany as a metalworker on the terminal project, but listed four completely different contractors for glass work and clock work. I am awaiting Untapped Cities as their journalists have further evidence that makes it clear it is not a Tiffany work. Until then, this myth cannot be fully busted with a reliable source.

The third "fact" is a little trickier. All good lies have some truth to them. The M42 sub-basement and power station actually was an area of concern during World War II, according to reputable author Sam Roberts. Its entrances were patrolled by armed guards, and the space was removed from any floor plans of the building. He even claims the saboteurs met in the terminal, by its information booth and in its newsreel theater. These facts are themselves somewhat questionable, though the reliable source merits their inclusion in the M42 article. But any ideas of a failed sabotage event taking place there are debunked by Roberts in his Grand Central: How a Train Station Transformed America. The more obvious falsehood is about secrecy: the station was far from secret, it was even advertised! It saw an incredible amount of press coverage over the century.

The fourth myth is perplexing. Every source states something similar, but different. It is a plain fact that several of the constellations are correct, and some are reversed, along with the overall arrangement on the ceiling. So the ceiling is neither fully correct or fully backwards. A pamphlet from when the terminal opened claimed "it is safe to say that many school children will go to the Grand Central Terminal to study this representation of the heavens." So at least some of the New York Central Railroad's staff believed the mural to be correct. What's great is you can read The New York Times' March 1913 account of a Westchester commuter who noticed the constellation mistakes, not even a month after the station opened in 1913. I believe the Vanderbilts claimed the mural to represent a "divine perspective" as a cover-up for such a literally massive mistake. So there's never been agreement over what's incorrect or why, and the only way I imagine finding the truth is if some of the artists, painters, or astronomers had some private notes or journals. All of the explanations either involve disinterest in the technicalities, finger-pointing, or the boisterous claim that it was intentionally incorrect.

My takeaway is, why even bother making up or believing in such tall tales? The strongly-documented history of the terminal is an interesting story enough. Sometimes the truth is stranger than fiction.