Taal Lake is a freshwater lake in the province of Batangas, on the island of Luzon, Philippines. The lake is situated within a caldera formed by very large eruptions between 500,000 and 100,000 years ago. It is the country's third largest lake. The active Taal Volcano, which is the one responsible for the lake's sulfuric content, lies on an island in the center of the lake, called Volcano Island.

Taal Lake was once just an arm of Balayan Bay. However, after a series of major eruptions in the 16th century, the lake was closed off from the sea by newly-formed land bridges. Taal Lake's sole connection to the sea narrowed down into its sole draining river, the Pansipit River. Several centuries of precipitation have diluted the lake's once-saline waters into pure freshwater.

 

Succeeding eruptions buried numerous lakeside towns. Presently, only three towns are on the lake's shore. Old lakeside towns with buildings and walls are reported to be seen under the lake's waters.