The Kensico Reservoir is a reservoir located in Valhalla, New York that was put into service in 1915. It is about 3 miles (4.8 kilometres) north of White Plains, New York, and about 15 miles (24 kilometres) north of New York City. It was formed by impounding the Bronx River, but receives most of its water from other places. For instance, it also shares water with Rye Lake, which is separated from the Kensico Reservoir by Great Island, an island in the middle of the lake/reservoir that used to be the top of a mountain. Along with the West Branch Reservoir and Boyds Corner Reservoir, it is one of only three reservoirs within the Catskill/Delaware system that is not in the Catskill Mountains region. http://en.wikipedia.org/wiki/Kensico Reservoir
The ranking score is used to determine how "popular" a trip or location is. It is calculated based off of a weighted average of the number of reviews and the user ratings. For example, a location with 2 reviews and an average rating of 5 will have a lower "ranking score" than one with 10 reviews and an average rating of 4. This is because even though the first location has a better average rating, it has not been reviewed as much as the second location, so it is not as "popular". In the future we may modify the ranking score to take in additional factors, such as the number of views, comments, and photos.