Question: What river is the location of the PENREN across from?

Context paragraphs:
Roanoke River Light: The Roanoke River Light is a historic, decommissioned lighthouse, located on the waterfront of Edenton, North Carolina.  The lighthouse once stood in Albemarle Sound at the mouth of the Roanoke River, across the Sound from its current location.  The only surviving screw-pile lighthouse in the state, it has since been moved twice, and a replica of a predecessor light has been erected at a fourth location.

The Pentagon: The Pentagon is the headquarters of the United States Department of Defense, located in Arlington County, Virginia, across the Potomac River from Washington, D.C. As a symbol of the U.S. military, "The Pentagon" is often used metonymically to refer to the U.S. Department of Defense.

Main Street Bridge (Charles City, Iowa): The Main Street Bridge is a historic structure located in Charles City, Iowa, United States.  It spans the Cedar River for 248 ft .  Before a bridge was built at this location local citizens would cross the river by way of a ferry, at a ford in summer, and across the ice in winter.  The first bridge at this location was washed away in a flood while it was under construction in 1858.  The second bridge was completed in 1864, and it was destroyed in a flood two years later.  A temporary bridge was completed in 1867, and it was replaced by a truss bridge in 1870.  It was used for 40 years despite an engineer's study in 1892 that suggested it be condemned.  The Floyd County Board of Supervisors approved a replacement bridge in 1908.  The old bridge was moved to a new spot five blocks downstream, but contract problems delayed construction of the new bridge.  Advance Construction Company of Waukesha, Wisconsin was finally awarded a contract in March 1909.  The three span concrete filled spandrel arch bridge was designed by their designing engineer G.W. Miller.  It was completed in 1910 for about $40,000, which was paid for by the county and the city.  The bridge was listed on the National Register of Historic Places in 1999.

Green Island, Nebraska: Green Island, 10.5 square miles of land in northwestern Cedar County, Nebraska bordering the Missouri River across from Yankton, SD, was home to Strahmburg a former town on the island.  Green Island and Strahmburg have had their names used interchangeably over the years because, in part, the post office in Strahmburg was officially designated as Green Island.  Supposedly Green Island acquired its name came the color of its lush vegetation.  Though called an island, it was physically connected to Nebraska by a swampy, low-lying area along its southern edge.  Both were destroyed by the Great Flood of 1881 on the Missouri.  Their history is better understood knowing the braided, meandering, flood-prone history of the Missouri River in that area.  Completion of Gavins Point Dam in 1957, 5 miles upriver from the former location of Strahmburg, greatly reduced the risk of floods on the river.  Today the Missouri National Recreational River, 59-miles between Gavins Point Dam and Ponca State Park, has restrictions on commercial development.  Early maps indicate the presence of numerous islands some of which, like Green Island, no longer exist.

Wolf Point, Chicago: Wolf Point is the location at the confluence of the North, South and Main Branches of the Chicago River in the present day Near North Side, Loop, and Near West Side community areas of Chicago.  This fork in the river is historically important in the development of early Chicago.  This was the location of Chicago's first three taverns, its first hotel, Sauganash Hotel, its first ferry, its first drug store, its first church, and the first bridges across the Chicago River.  The name is said to possibly derive from a Native American Chief whose name translated to wolf, but alternate theories exist.

Little America Hotels: Little America is a chain of four hotels in the western United States.  The first Little America, called Little America Wyoming, is 24 mi west of Green River, and 35 mi west of Rock Springs on Interstate 80.  Built in 1952 along the old alignment of U.S. Route 30 which was also the Lincoln Highway, the first road across America, the property began with two fuel pumps, a 24-seat café, and 12 guest rooms.  Today the location has 140 rooms and expanded gas pumps for both truck drivers and travelers.  For a number of years this location had the world's largest filling station based on the number of pumps in operation — 55 in all.

Olive City, Arizona: Olive City, or Olivia, was a short-lived town, steamboat landing, and ferry crossing on the Colorado River in what was then Yuma County, Arizona Territory, from 1863 to 1866.  It was located on the Arizona bank of the Colorado River, 1 mile above its rival Mineral City and 1/2 mile above the original site of Ehrenberg, Arizona, 3 miles southwest of the location of La Paz.  The GNIS location of Olive City (historical) is indicated as being in La Paz County, Arizona, but its coordinates in the present-day now put it across the river just within Riverside County, California Olive City was named after Olive Oatman who had been, with her sister, survivors of the massacre of her family and a captive of the Yavapai until purchased from them by the Mohave who they lived with for several years.

Waterloo Village, New Jersey: Waterloo Village is a restored 19th-century canal town in Byram Township, Sussex County (west of Stanhope) in northwestern New Jersey, United States.  The community was approximately the half-way point in the roughly 102-mile (165 km) trip along the Morris Canal, which ran from Jersey City (across the Hudson River from Manhattan, New York) to Phillipsburg, New Jersey, (across the Delaware River from Easton, Pennsylvania).  Waterloo possessed all the accommodations necessary to service the needs of a canal operation, including an inn, a general store, a church, a blacksmith shop (to service the mules on the canal), and a watermill.  For canal workers, Waterloo's geographic location would have been conducive to being an overnight stopover point on the two-day trip between Phillipsburg and Jersey City.

Red River Trails: The Red River Trails were a network of ox cart routes connecting the Red River Colony (the "Selkirk Settlement") and Fort Garry in British North America with the head of navigation on the Mississippi River in the United States.  These trade routes ran from the location of present-day Winnipeg in the Canadian province of Manitoba across the Canada–United States border and by a variety of routes across what is now the eastern part of North Dakota and western and central Minnesota to Mendota and Saint Paul, Minnesota on the Mississippi.

Pentagon Renovation Program: The Pentagon Renovation Program or PENREN was a long-term project by the United States Department of Defense to perform a complete slab-to-slab renovation of The Pentagon in Arlington, Virginia.  The program began in the 1990s, and was completed in June 2011.

Supporting paragraphs: Pentagon Renovation Program The Pentagon
Answer: the Potomac River