aircraft anchored balloon cable checks circular colors colours control controlled duty-pilot engineers fabric filled flight-operation gondola height helium helium-balloon high inspected inspections large limited mesh metal-cable metal-line monitored monitoring motion movement net passengers pilot piloted registered ride safe safety secure secured sights sightseeing Singapore tethered tourists views weather-limits wind-limits abstract angled angles appearance architectural architecture building buildings city contemporary contrast contrasting corners distinctive edged edges elements exterior external framed frames geometric geometric-shapes glass gray grey high-rise light linear lines modern patterned patterns perspectives sharp sharp-cornered sharp-corners straight-up-and-down surface surfaces textured textures wall walls windows animals Asian-elephant-subspecies big browsers close color colored colour coloured communicating connected connecting downpour elephant-hide elephants elephas-maximus-indicus enclosure endangered Females grazers habitat-loss hair hairy heavy herbivore hide Indian-elelphants intelligent mammal megaherbivores rain raining skin strength strong style texture tough trunks tusks wet wrinkled wrinkles wrinkly zoo