Year after year, Washington DC routinely rates as one of the nation’s top 10 event destinations, what, with its rich history, its role as the nation’s seat of power, and the abundance of attractions, amenities, and all.If you’re a frequent DC conference goer or live in the area as I do, chances are you’re already well aware of the area’s “must sees:” The Smithsonian Museums (all 19 of them), the National Zoo,The Capitol Building, The White House, The National Archives,The Supreme Court, The Washington Monument , Great Falls National Park, and Mt.Vernon.Which begs the question, where do you send the event-goer or local who's been there and done that—having seen all there is to see and done all there is to do?Simple. Send them off the beaten path. Here are a few of my favorite little-known gems that are every bit as captivating as the “must see,” particularly if you’re into history: 4-D Theatre at Mt. VernonWhile Mt. Vernon, George Washington’s sprawling 18th century plantation on the banks of the Potomac, is one of those “must see” venues from the list above, the wizardry of the 4-D Theatre in its world-class museum rates its own callout. The theater features a wide-aspect ratio screen, 4k resolution projector, 9.2 channel surround sound, and, without giving away the 4-D special effects entirely, let’s just say snowball throwing is strictly frowned upon. National Museum of the US NavyThe National Museum of the US Navy is one of the area’s best-guarded secrets. No, literally. It’s smack dab in the middle of the US Navy Yard, an active naval base on the Capitol waterfront. To gain admittance, you have to pass through a guard post and then make your way to a screening desk to present your driver’s license.But, assuming you’ve never been convicted of a felony, those are the only hurdles coming between you and this incredible museum. From the near perfect hole bored through the 26-inch thick armor plating of the Japanese Battleship Yamamoto (made by a 16” armor-piercing shell during ballistics testing following WWII) to the 50-foot long bathyscaphe Trieste, the deep-water research vessel that, in 1960, set the record for the deepest manned dive (A record that held until 2012, when James Cameron dove even deeper)—the museum is one of the area’s finest. Yet, most locals don’t even know it exists. Shark tooth hunting at Purse State ParkNot long ago (geologically speaking) much of the Washington DC metropolitan area was covered by shallow seas and inhabited by sharks. Today, a leisurely hour’s drive from Washington to Purse State Park takes you back nearly 60 million years to the Paleocene Era when sharks represented 90% of the Atlantic’s fisheries.All these millennia later and the ferocious predator’s presence can still be felt in the form of the dozens of shark teeth you’ll easily find in the surf along the park’s narrow beach.“Why are shark’s teeth so plentiful there?” you ask. Keep in mind, then as now, sharks had between 5-15 rows of razor-sharp teeth. As one tooth fell out, another rotated forward to take its place. As a result, any given shark could be expected to produce and shed as many as 50,000 teeth in its lifetime. Now, when you consider that nearly every fish in the sea was a shark…well…it becomes a bit of a mouthful. It just so happens that the altitude of this particular bend in the Potomac coincides with the depth of sediment the teeth were deposited eons ago, so as the river erodes the cliff-side, thousands of new (fossilized) teeth are exposed daily. The continuous refreshing of new fossils means chances are you won’t leave the park empty handed. The National Museum of Health and MedicineFounded by the US Army’s Surgeon General during the height of the Civil War, the National Museum of Health and Medicine in Silver Spring, Maryland is unlike any museum you’ve likely seen before, filled with artifacts you’re unlikely to come across anywhere but a warzone. Among other things, the museum chronicles in graphic detail the incredible strides medicine and surgery have taken since the Civil War in treating traumatic battlefield injuries. The fact it does so with actual specimens motivated the Washington Post’s Sadie Dingfelder to describe it as, “a fascinating nightmare.” Yet, for the countless men and women in uniform who owe their lives to the medical advances archived in the museum, undoubtedly there’s nothing nightmarish about it. College Park Aviation MuseumShortly after Wilber or Orville Wright’s historic first powered flight in Kitty Hawk, North Carolina, the US Army realized the strategic advantages airpower could provide. As a result, in 1909 it hired the two brothers to train military aviators at what became the nation’s very first military airfield, in College Park, Maryland. From a convincing Orville Wright animatronic and a wing-bending Wright Flyer flight simulator to static displays of the nation’s earliest powered aircraft and lessons in the physics of flight, the little museum packs in a lot of informative content and hands-on displays worthy of the role it played in the history of aviation. The National Museum of the Marine CorpsJust forty minutes from DC, adjacent the Marine Corps base in Quantico, Virginia, The National Museum of The Marine Corps is one of the most captivating and thoughtfully crafted museums anywhere. Designed by architect Curtiss W Fentress, the building itself evokes the iconic photograph of the Marines planting the US flag on Iwo Jima during World War II. Inside, the museum continues to wow with static displays of airplanes, landing craft, tanks, helicopters, artifacts, and ordinance.The layout of the museum follows the history of the Marine Corps from its formation in 1775 during the Revolutionary War. It takes you through breathtaking life-like dioramas of the Corps’ legendary battles, from the epic battle of Belleau Wood to Vietnam and the close quarter's combat of Khe Sanh.The museum stresses ultra-realism, to the point you may want to bring a jacket and stay low as you enter the battle of the Chosin Reservoir, recreating the moment the Chinese entered the Korean War as the US Marines fought for their lives on a snow-covered mountain top. This exhibit gives the term “Cold War” chilling new meaning if you get my drift.