Here is the Potomac River looking south from Maryland to Virginia, just six miles north of my apartment.
Next to the river on the Maryland side is the C & O Canal. I'm standing in front of locks that let boats travel up and down this man-made freightway.
http://www.nps.gov/choh has more info about this national park
The towpath next to the canal has been converted to a long bike trail, with one end about 9 miles southeast of here at the National Mall in Washington.
I was surprised at how narrow the locks were.
At each set of locks was a little house for a lockmaster and his family. Some such families made a little extra money by growing a garden and selling food to passing boats.
The canal and trail at this point had been breached by hurricane floods a few years ago.
Other parts of the canal appear much as they did when it was built in 1830.
http://bikewashington.org/canal/ will tell you more about the C&O Canal Trail.
The gates of the canal had to be strong enough to hold the water but light enough for someone to turn the wheel to open and close the gates. If a lockmaster was not careful, he could break his arm or sink a boat.
A blue heron. I was told many of these big birds live along the Potomac river and the canal. I also saw a deer, a fox, and some turtles along the canal.
The bike trail runs from Washington DC 184 miles northwest, with the canal on one hand and the river on the other hand, though not always this close. At trail's end near Cumberland, MD, you can continue on another bike trail 146 miles to Pittsburgh, PA.
I explored up to the little town of Cabin John, and stumbled across a community center fund-raising dinner serving crabs. That is, the people were friendly; they and I ate the crabs. There are little wooden hammers at each table to crack open the crabs. It sounded like a hundred carpenters at work. http://www.cabinjohn.org/pages/history.htm
