River Thames frost fairs were held on the tideway of the River Thames at London in some winters between the 17th century and early 19th century, during the period known as the Little Ice Age, when the river froze over.

River Thames Frost Fair

That would be the River Thames.

The River Thames is the major river through London, cutting right through the middle of the city. There are many other rivers in London, such as the River Lee (or Lea) and the River Brent.

The river Thames (pronounced temz)