res·er·voir | \ ˈre-zə-ˌvwär
1. a place where something is kept in store: such as
: an artificial lake where water is collected and kept in quantity for use, a part of an apparatus in which a liquid is held or a supply store.
In the article “The Way We Live No: 11:11:01; Lost and Found by Colson Whitehead, the author states, “That Bryant Park used to be a reservoir.”
In this sentence, the author is saying that people think that Bryant Park, New York used to be an area where things, like water and animals, were kept in.