Great Falls of the Potomac in the blue hues of first light, while a great blue heron contemplates breakfast.

The flooded waters of the Potomac River cascade over the drops at Great Falls.

Daring kayakers plunge over Great Falls in timed races during Potomac Whitewater Fest.

Daring kayakers plunge over Great Falls in timed races during Potomac Whitewater Fest.

A skin of Potomac ice grasps Memorial Bridge, with the moon and Arlington House in the background.

The Washington Monument reflects in the semi-smooth ice of the frozen Potomac River.

A rower and small passenger enjoy the evening color, with the Air Force Memorial in the background.

The Lee Mansion witnesses dawn over the Potomac, as the moon sets behind it.

A long exposure draws a graceful arc from the light trails of a jet departing Reagan National Airport.

The Potomac River reflects the blue sky overhead, as the orange dawn lights the horizon behind the monuments.

Key Bridge marks the Potomac River's grand entrance to downtown Washington DC.

An arch of Francis Scott Key Bridge seems to leap toward the Virginia Shoreline. Georgetown and The Watergate are clear in the background.

The first light of dawn illuminates the gleaming towers of Rosslyn, Virginia.

Sunset fades in the west as evening lights reflect in the Potomac River.

The gateway to Georgetown rests quietly beside the Potomac before dawn.

The gateway to Georgetown decorates the Potomac waterfront with lovely lights on its boardwalk.

The gracefully-curving shoreline of the Potomac River is mimicked by the bike path and GW Parkway.

A pair of sweep boats, each with 8 rowers plus coxswain, drill on the Potomac in late afternoon sunshine.

Roosevelt Bridge seems busy, glowing orange, while Memorial Bridge is serene in its blue and white.

The full moon rises orange as twilight settles over the Potomac River in Washington DC.