The term 'Chain of Hills' refers to a series of hills or mountains that are connected together. The two crossword solutions for this term are 'SIERRA' (6 letters) and 'RIDGE' (5 letters). SIERRA is a Spanish word meaning mountain range, while RIDGE is a geological term referring to a long, narrow elevation of land that is higher than the surrounding area. Together, these two words describe a chain of hills or mountains that are connected together.