WARSAW, Poland (AP) — Warsaw is having a treasure hunt — exploiting the record low level of the Vistula River to find pieces of historic bridges and boats amid the discarded tires and broken glass littering its banks.

It's all part of city authorities' goal to turn the free-flowing river into a major tourist and sports attraction.

After a wave of unusually high summer temperatures, the Vistula, which flows 1,047 kilometers (651 miles) from the Beskidy Mountains to the Baltic Sea, is at its lowest level since measurements started in late 18th century. Only last year, and especially in 2005, the whimsical river had threatened to overflow its banks in Poland's capital after heavy rains.

Now in Warsaw, Poland's main river has dropped to about 50 centimeters (20 inches) at some places from its usual average depth of 200 centimeters (6 ½ feet), stalling flat-bottomed barges and tiny tour boats, exposing both treasures and eyesores.

About 300,000 zlotys ($79,000) is being spent on removing waste and retrieving elements of the city's 18th- century wooden Poninski Bridge, which was destroyed in 1806, and some shattered stone benches from the early 20th-century Poniatowski Bridge, which Germany's Nazis blew up in 1944.

Archeologists also say a carved log of soaked wood that was found could be a piece of a medieval boat.

Promoting the cleanup, top Warsaw officials joined hired cleaners Wednesday in removing broken bottles, umbrellas and metal pieces from the exposed river bed. The cranes needed to do some of the heavier work have to wait for higher water.

"We are taking a positive look at this situation and seizing the opportunity to do some cleaning," deputy Warsaw Mayor Michal Olszewski said.