A lake: a relatively large body of water surrounded by land, often natural and sometimes a tourist attraction.
夏休みに家族で湖へキャンプに行った。
I went camping at a lake with my family during summer vacation.
その湖は周りの山々が写ってとても美しい。
The lake reflects the surrounding mountains and is very beautiful.
湖畔を散歩しながらコーヒーを飲んだ。
I drank coffee while walking along the lakeside.