Yamanaka Lake
Proper noun
やまなかこ
安物のカメラで撮ったにしては、山中湖の写真すごく綺麗に撮れてるじゃん。
Given how cheap the camera was, all the pictures of Lake Yamanaka turned out beautiful.
The mountain middle lake is lake Yamanaka, a famous and very nice lake in Japan. It's also a lake that will help you to learn the lake kanji reading better.
The reading is the kun'yomi readings of 山 and 中, then the on'yomi reading of 湖.