This is the 635th most frequent Japanese word.
千
"千" means "thousand" in English.
In this sentence, "千" is used to represent the numerical quantity of "a thousand."
その湖は千人が訪れる観光地だ。
That lake is a tourist spot visited by a thousand people.
Here, "千" is part of the term "千秋楽" (senshuraku), which refers to the final day of traditional art performances or tournaments. The "千" adds a sense of grandness.
昔、千秋楽で相撲を見たことがあります。
Long ago, I watched sumo on the final day of the tournament.
In this context, "千" is used metaphorically to symbolize a large, significant number, as in the creation of "千羽鶴" (senbazuru), a traditional symbol of peace and hope.