The mayor made the declaration in 2004.

The world's largest mountain carving could fit all of Mount Rushmore inside it many times over.

This whimsical seashell-shaped place of worship was designed to blend into its surroundings.

The old building has been restored to its 1907 appearance.

One of America's oldest continuously operating hotels offers a blend of rich history and historic architecture in the heart of Annapolis.

The oldest surviving one-room schoolhouse in Montgomery County, Maryland.

FDR's Art Deco hospital tower was hopelessly inefficient.

She stares out across six lanes of traffic, clutching a musket and infant with determination.

The bridge's highly-contested plaque (once again) honors Confederate President Jefferson Davis.

Although built to generate electricity for Marylanders, this dam has become an all-you-can-eat buffet for American bald eagles.

The tallest The Church of Jesus Christ of Latter-day Saints temple in the world soars above the Beltway.

A lawn full of retired spacecraft on display at one of NASA's first research labs.

Once home to seven different roller coasters, Glen Echo has undergone many transformations since its founding in 1891.

An oft-overlooked, magically musical monolith that stands majestically between Arlington Cemetery and the Iwo Jima Memorial.

These unusual rooms on wheels are holdovers from the 1960s.

This isn't your average roadway—it's actually a National Park and a transportation pioneer.

The romance of early commercial flight still fills this Art Deco destination.

At Washington's Dulles Airport is a satellite museum (no pun intended) with three quarters of a million square feet of aircraft history.

The story behind the mysterious symbol painted in front of the historic university's famous Rotunda.

A former major munitions plant that has been converted into a sprawling art space.

Thomas Jefferson's estate is home to hundreds of varieties of historic fruits and vegetables.

This historic mansion was built as a symbol of love between a husband and wife.

An organ located deep within a cave, whose "pipes" are the geological features of the cave itself.

Colloquially known as "the lynching memorial," this is the United States' first memorial to the victims of racial terror at home.