The Arboretum Terrace. The Arboretum terrace, at almost 300m long, is the most striking feature of this park, which was opened in 1872 to the design of Edward Milner. The focal point of The Terrace was an elegant iron and glass pavilion which stood here and contained a display of exotic plants. Having worked for many years with Sir Joseph Paxton, designer of The Crystal Palace (1854). Edward Milner would have been very familiar with design of ornamental glasshouses