Sydenham is a South East London suburb in the London Boroughs of Lewisham, Bromley and Southwark. Sydenham was located in Kent until 1889 when the County of London was formed, additionally, in 1965 Sydenham became part of the current London Boroughs. The area was one of the first in Southern England to have a railway station, opening 1839 by the London and Croydon Railway. Sydenham is the location where the Crystal Palace from the Great Exhibition was relocated in 1854.
More information on the Wikipedia page [1] and the Hidden London page [2].