Stand before the Smithsonian Institution Building, a Hogwarts-like spire sandwiched between the Washington Monument and the US Capitol, and you might just get a sense of how deeply rooted the Smithsonian Institution is in our nation’s heritage. This building, often referred to simply as “the Castle,” now contains the tomb of James Smithson, who in 1846 got the ambitious project off the ground with a generous donation of $500,000.

Back then, the plan was to erect a museum that would focus on natural history, art, and objects “of foreign and curious research.” But what began as a wealthy UK scientist’s pet project has today mushroomed into the world’s largest museum complex, with a staggering 19 museums and galleries, nine research facilities, and the largest known collection of museum objects (138 million to be exact-including 1.5 million books).

Oh, and there’s even a zoo. Because what brings home the concept of biodiversity better than seeing tumbling giant pandas, slithering reptiles, and leaping tiger cubs up-close? Originally conceived to educate the public about animal conservation (particularly for rapidly disappearing American wildlife), the facility has since spread across 163 acres, housing over 1,500 animals.

If you’re visiting the D.C. Metro area and somehow manage to avoid even the briefest pass through the Smithsonian’s vast exhibit halls, shame on you. Truth be told, it would be difficult not running into at least one of the facilities during your stay-the majority of the Smithsonian Institution’s buildings sit along the National Mall, and remain open every day of the year except December 25th. The best part? Admission to almost all of them is free.

Officially opened in 1855 with the “Castle” (today, the building houses the museum’s main information center, a useful starting point for any visitor), the Smithsonian Institution today operates with a staff of 6,511; though, its total network of volunteers-instrumental in bringing the exhibits to life for younger students-numbers well over 12,000.

While no single theme can be applied to the Smithsonian Institution as a whole-there are simply too many exhibits, covering a broad range of fields-its collection is riddled with important cultural artifacts.

For example: Peep the star-spangled banner, otherwise known as the “original” 1813-sewn American flag, on view at the National Museum of American History. Nearby, the Spirit of St. Louis, which completed the first solo, nonstop transatlantic voyage in 1927, rests at the National Air Space Museum.

At Mitsiam Cafe, you can feast on native dishes-like fry bread and corn totopos -inspired by indigenous cultures from around the Western Hemisphere.

In the mood for something more deeply historic? Over at the National Museum of African American History and Culture, which celebrated its grand opening last month, you’ll find an original copy of the Emancipation Proclamation, the 1863 document signed by Abraham Lincoln, that eventually led to the abolition of slavery across the United States. In the same building, glimpse a hymnal once owned by Harriet Tubman.

Of course, there are the ruby slippers that Judy Garland actually wore during the 1939 filming of the Wizard of Oz. And in the Natural History Museum’s Gem Hall, gaze in awe at the Hope Diamond, an antique 45.52-carat stone once purchased by King Louis XIV of France, and famous for its rich blue iridescent hue. But whether it’s cuddly pandas, or airplanes, or jewels you show up for, you’ll leave with a deeper appreciation of the impact U.S. culture has had on the wider world.