Yesterday we had the pleasure of visiting The Frick Collection, which, if you don't already know, contains steel magnate Henry Clay Frick's art collection, all housed inside of his East 70th Street mansion (inspiration for the Avengers mansion!). The home was designed by Thomas Hastings and was constructed in 1913, though in the 1930s was altered by John Russell Pope to ready it for use as a public institution. While the public spaces of the mansion are enough to give anyone real estate envy... what we were interested in was what was behind closed doors. With an old home like this you know there are some secret spots—click through to see what we found during our visit. And below, some fun facts we learned during our journey:

Helen Clay, Frick's daughter, was the one to erect a library on the vacant lot next door (6-8 East 71st Street) to catalogue her father's collection. For a time, she housed this in the bowling alley due to lack of space.
The bowling balls have since been replaced from ones Frick himself used, which had just two holes for fingers, and were significantly heavier than today's standard balls. (More on the bowling alley in The Frick's members magazine, which we've included in the image gallery.)
In case you were wondering, no, this is not the bowling alley that was used in There Will Be Blood.
H.C. Frick and his wife were supposed to be on the Titanic (something that has been confirmed throughout the years), but his wife twisted her ankle and they stayed abroad for a few more days. If he had boarded the ship, there would be no Frick mansion today!
For the most part, the paintings in the galleries are arranged in the way Frick wanted his visitors to see them.
The fountain room at The Frick may be the most photographed public space in the museum, but that feature (with its sunken pool) wasn't there when Frick was alive. Before he died it was an outdoor driveway (which did contain a smaller water feature).
There are no ghosts at The Frick! Although, we were told this when we didn't even ask, so perhaps our host was protesting a bit too much?

And in more current events: they are in the process of adding a sculpture gallery, which will have glass walls opening on to the garden to let in light. Currently there are no plans to open the garden up, however.