The Lac à l'Anglais is a lake located west from the city center of Chamonix. There are 2 other lakes nearby called the Lac des Gailland and people often just refer as all these lakes and the nearby climbing wall as Lac Gaillands. The lake is artifical and was built at the end of the 19th century by Lord Sinclair. John Sinclair frequently visited Chamonix and bought the land where the lake stands today in the year 1886. He then proceeded to create the lake and the nearby structures and a artificial cave as a tourist park. As such the nearby ruins are not of an old castle any other real structure. They are to be thought of more as garden oranaments. 

The lake is very pretty and its a popular destination for tourists and locals alike. The biggest outdoor climbing wall near Chamonix is located right at the end of the lake and there is also a snack bar and an accro park nearby. The Petit Balcon Sud runs right above it and provides an easy way of visiting the Lac Gaillands area as part of a hike or run.