Epic Circles - Numberphile (YouTube)
Pappus chains, circle inversion and a whole lot more in this EPIC video with Simon Pampena.- Willapa River (Wikipedia)
The Willapa River is a river on the Pacific coast of southwestern Washington in the United States, approximately 20 miles (32 km) long. It drains an area of low hills and a coastal plain into Willapa Bay, a large estuary north of the mouth of the Columbia River.