New York is full of hidden signs and symbols — if you know where to look. John Tauranac does. The author of “Manhattan’s Little Secrets” (Globe Pequot) is a certified tour guide and map designer who also teaches architectural history at NYU’s School of Professional Studies. In his new book, he highlights 120 details on (or in) buildings and lays out their little-known backstories. Below, some of our favorite urban gems, many of them hiding in plain sight.

1. 1. Washington Square Park arch

   

   The small door on the side is permanently locked — and roof access verboten — because of a revolutionary party more than 100 years ago. On Jan. 23, 1917, violinist and art apprentice Gertrude Drick discovered that through a doorway on the west side of the arch were 101 steps that wound around circular stairway to the roof. She “thought it would be a lark to sneak up to the roof one night and declare the secession of the Village from big business and small minds.” Attendees included artists John Sloan and Marcel Duchamp and three actors. Amid balloons, candles, sandwiches and beverages, Drick announced a “Free and Sovereign Republic of Greenwich Village.” Since that night, the door has been locked. No rooftop shenanigans allowed!

2. 2. The Public Hotel, 215 Chrystie St.

   

   The Diego Rivera artwork that should have hung behind the reception desk at 30 Rockefeller Center was destroyed decades ago. Now it’s been brought back to life, stretching across the wall of a Lower East Side hotel. The Rockefeller family, who were patrons of modern art, commissioned Rivera to paint the fresco in 1934. Controversial elements in “Man at the Crossroads” included: a portrait of Lenin; a “Workers of the World Unite” banner; police using cudgels against peaceful protesters; women playing cards; and people drinking martinis and smoking cigarettes. Nelson Rockefeller was not happy. Rivera was paid in full and ordered to leave. The unfinished work was covered, and a year leader, “wreckers move in with sledgehammers and knocked the fresco to smithereens.” Hotelier Ian Schrager bought the rights to the image from the Diego Rivera foundation and had it recreated at seven by 18 feet, or half the size of the original. It’s now in the Public Hotel’s bar, appropriately called Diego.

3. 3. Bennett Memorial, Herald Square

   

   The publisher of the New York Herald was obsessed with owls. Well in advance of his death, James Gordon Bennett Jr. envisioned a gigantic hollow owl — some 125 feet high, only 26 feet shorter than the Statue of Liberty — on top of an almost-as-massive pedestal. His coffin would hang inside its head. The mausoleum never came to fruition, but a statue of Minerva (goddess of wisdom) whose stone base is topped by two small owls (her avian associates) did, dedicated in Herald Square in 1895. On its back is a small circular plaque with another owl, resting on a crescent moon, with the words “La nuit porte conseil.” Though it literally translates to “The night bears counsel,” the idiomatic meaning is “Sleep on it.” Bennett Jr., who drunkenly peed into a fireplace he mistook for a urinal one New Year’s Eve at his fiancée’s house, clearly didn’t take his own advice. The engagement was called off.

4. 4. Fashion Tower, 135 W. 36th St.

   

   As the Garment District sprung up around Seventh Avenue south of Times Square, famed architect Emery Roth was tapped to design a 17-story building to house showrooms for wholesale-fashion companies. Grand terra cotta panels adorned with two peacocks crown both its main entrance and its freight entrance. Why spend so much on a byway for service staff? First, it was the “It building” of the industry at the time, called simply Fashion Tower, a name that persists to this day. Second, once a mold for the first panel was made, it was quite easy to manufacture another one for added effect.

5. 5. Henri Bendel, 714 Fifth Ave.

   

   French perfumery House of Coty peddled fragrances from this prime Midtown spot. Its head, Francois Spoturno, enlisted famed glassmaker Rene Lalique to design bottles. The collaboration was such a success that Spoturno also had Lalique craft three stories of frosted glass for its showroom, an art nouveau depiction of flowers and vines climbing the facade. House of Coty moved out in the 1950s when its lease expired. The building was nearly torn down to make way for a skyscraper — until historian Andrew Dolkart rediscovered and publicized the glass panels in the 1980s and the building — now home to Henri Bendel — was landmarked (and therefore saved) as a result.

6. 6. The 'Poseidon' Station, Northwest corner of West 72nd Street and Central Park West

   

   The chief architect of the subway in the early 20th century, Squire Vickers, loved flourishes. His budget, sadly, didn’t often allow for them. As Vickers prepared to open a subway station by the Dakota in 1932, he got creative. The 1884-built Dakota has a “dry moat” surrounded by a cast-iron fence ornamented by sea monsters with a ferocious bearded man in the center widely believed to be Poseidon, god of the sea. A standard subway entrance at the time would have destroyed or obscured a section of fencing, so Vickers incorporated it into a custom entrance instead, “thereby saving it for posterity and saving the city some money at the same time.”

7. 7. St. Thomas Church, 1 W. 53rd St.

   

   From 1913 to 1921, betrothed women in white entered St. Thomas’ Church on their wedding days via a small door to the left of the main entrance so they could slip into the church unseen before their ceremonies. Above the entrance is a statue of St. Joseph, patron saint of marriage; above him are two curlicued carvings. The left side’s is the symmetrical “lovers’ knot,” while the right’s looks like a gussied-up dollar sign. It was only in 1921, when word of the dollar sign’s presence spread, that opposition sprung up. Architects Cram, Goodhue & Ferguson defended their facade: the knot “symbolized true love and the right kind of marriage,” while the dollar sign “tells the story of the loveless marriage, the marriage for money.” Onlookers came to gawk at the brazen callout at the house of worship of a wealthy congregation.

8. 8. ‘Holdout’ house, 134 E. 60th St.

   

   In the mid-1980s, as the Cohen Brothers real-estate development firm assembled land to build an office tower on Lexington Avenue between 59th and 60th streets, they encountered one obstacle: Jean Herman, who refused to leave her rent-controlled walk-up apartment in a brownstone between Lexington and Park. She was paying $168 a month; Cohen Brothers offered her a comparable apartment rent-free as well as $650,000 cash. Five other tenants in the building were successfully bought out — but not Herman. So while all the surrounding buildings were demolished to make way for 750 Lexington Ave., workers went ahead sliced off Herman’s building’s top floor and painted the facade to match the new tower. She died in 1992, but evidence of her holdout still exists, jutting out the side of 750 Lex.

9. 9. St. Patrick’s Cathedral, Fifth Avenue between 50th and 51st streets

   

   On the lower part of the west wall of the south transept of glorious St. Pat’s is a stained-glass window that depicts a mere mortal. Gifted by cathedral architect James Renwick Jr., it shows himself, clad in a black tunic, gesturing to an unrolled scroll of his plans for the proposed cathedral to Archbishop John Hughes. Meanwhile, red-robed John Cardinal McCloskey stands to the side, holding a different set of plans. Renwick’s original designs for the cathedral — which included a central spire, a stone ceiling, flying buttresses and individual chairs rather than pews — didn’t come to fruition because of budgetary constraints and McCloskey’s influence. Renwick’s eye-rolling exasperation is evident in the motif.

10. 10. Inspiration Point, Henry Hudson Parkway (northbound side) at about West 190th Street

    

    Early 20th century New Yorkers out for a walk or drive along the Hudson would often stop at Inspiration Point to take in the breeze and views. Its popularity dictated that bathrooms be built, but the convention of the pre-Depression era was to make even the most humdrum facilities look grand. Hence the temple-like arrangement of Doric columns around a raised platform topped by a coffered roof with “comfort stations” tucked discreetly off to its side. It opened to much fanfare in 1925, but became dilapidated over time. A 1990s restoration axed the restrooms (which had been boarded up for years anyway) but brought the pavilion back to its original grandeur.