that are set back from the windows facing Bryant Park. , the Main Branch hosts 300,000 books in various reading rooms, though there are none in the central stacks themselves, due to the deteriorated condition of the stacks. There were proposals to demolish the central stacks to make room for the Mid-Manhattan Branch as part of the unrealized Central Library Plan in the early 2010s. , the library's trustees have still not determined how to use the abandoned stacks in the main building. Another 84 miles of stacks under Bryant Park was added in an expansion between 1987 and 1991. The Bryant Park stacks comprise two levels of climate-controlled storage areas. The stacks under Bryant Park contain 1.2 million books on what is called "Level 1", which was completed in the 1991 expansion. A second level of stacks below it, "Level 2", had not been finished when the 1991 expansion was opened. Another 2.5 million books were being moved from the NYPL's ReCAP warehouse in New Jersey to Level 2 , and when that was finished, the number of books in the Main Branch's stacks would rise to four million. The Level 2 stacks are called the "Milstein Stacks", after a major donor, and opened in January 2017. , the stacks also contain about 400,000 circulating volumes that are usually housed in the Mid-Manhattan Branch, which was closed for renovations until 2020. Books are delivered from the Bryant Park stacks to the reading rooms on the first through third floors using the "book train". The $2.6 million book delivery system was installed in 2016. It contains a conveyor belt and 24 small red carts emblazoned with the library's lion logo, which each carry up to of books between the stacks and the reading rooms. Each cart moves per minute and use gears to climb steep or vertical grades. Prior to the installation of the "book train", a Ferris wheel-style conveyor system was installed in the 1990s; it took ten minutes to retrieve a book using the old system, The "Ferris wheel" system, which was complemented by a dumbwaiter, itself replaced a 1920s-era book-delivery system and a 1960s-era dumbwaiter. The new book-delivery system was described as being twice as fast as the old system. Library Way Leading up to the Main Branch, on 41st Street between Park and Fifth Avenues, is a series of plaques known as Library Way. Library Way