The term 'Thames Landmark' can be summarized by the crossword solution of ETON. ETON is a prestigious independent boarding school located in the town of Eton, near Windsor, England. It is situated on the banks of the River Thames and is one of the most famous landmarks along the river. The school was founded in 1440 by King Henry VI and has educated some of the most influential figures in British history, including 19 British Prime Ministers.