A
榭 is one of the named structure types in classical Chinese garden architecture, alongside
亭 'pavilion',
台 'terrace',
阁 'tower', and
廊 'covered walkway'. It is specifically built on a raised platform and typically overhangs water - hence the very common compound
水榭 'water pavilion'. The set phrase
楼台亭榭 'multi-storey building, terrace, pavilion, kiosk' covers the whole vocabulary of classical garden buildings.