Knock knock, who's there?
In the world of Instagram, photographers run wild, capturing everything from the extraordinary to the ordinary. Doors would appear to fit in the latter category but Caryn Cullinan's Instagram account may make you re-consider how you look at entrances.
Seen here, a dramatic entrance in Barcelona, Spain.
@thedoorproject
Cullinan, 40, runs the @thedoorproject page on Instagram. She started it in May 2012 and has amassed an impressive collection of photographs of doors from around the world.
She says she's taken "thousands" of photos of doors in more than 66 cities.
Washington, D.C.
@thedoorproject
But what is it about doors that captured Cullinan's focus?
Her interest first revealed itself on a trip to Florence, Italy, where she started to gravitate toward doors. The interest quickly turned to a passion.
"There's a story behind every door," Cullinan told CBS News. "Wherever I am, I like to find a door that reflects the culture, and I love being there in the moment, capturing it and tagging it on my map."
Malibu, California
@thedoorproject
Cullinan resides in Colorado -- a state better known for its outdoors than its doors. But Cullinan still manages to find captivating entryways.
Denver, Colorado
@thedoorproject
While Cullinan has long been passionate about photography, her day job is in sales for a German company.
Her work requires her to travel to different cities, allowing her the opportunity to document foreign doors.
Hattingen, Germany
@thedoorproject
Her favorite doors tend to be from the places that are closest to her personal life. Doors from Korea are especially important to Cullinan because it's the birthplace of her son.
Seoul, South Korea
@thedoorproject
For Cullinan, the doors are much more than just an entry way -- they're an extension of culture. She points out that with a single photo of a door, one can almost instantly know where that door is from.
"It just tells a lot," she said. "Behind every door is a story -- a reflection of architecture and the city and the culture."
Harlem, New York
@thedoorproject
"Sometimes I see doors that are so elaborate or intricate or so large and I think why? Why is that door built the way it was?" said Cullinan.
Malibu, California
@thedoorproject
Cullinan has amassed more than 25,000 followers on Instagram. She says she started the hashtag #doorsworldwide that others also use to tag the photos they take.
San Francisco, California
@thedoorproject
Cullinan says there are several cities she'd like to visit next, including Mumbai.
"I can only imagine how interesting the variety of doors would be," said Cullinan.
Lyon, France
@thedoorproject
Her plans for her page include the possibility of creating a coffee table book - and of course, sharing her passion for #doorsworldwide.
Cullinan has launched a Kickstarter campaign in her goal to publish a photo book of her doors.
Austin, Texas