List of longest caves
List

System
Length
Location
Discovery
Associated parks, protected areas
Mammoth Cave
651.8 km (405.0 mi)
near Brownsville, Kentucky, United States
1791
Mammoth Cave National Park, also a World Heritage Site and International Biosphere Reserve
Sistema Sac Actun / Sistema Dos Ojos
360.5 km (224.0 mi)
near Tulum, Quintana Roo, Mexico
1987
none
Jewel Cave
324.9 km (201.9 mi)
near Custer, South Dakota, United States
1900
Jewel Cave National Monument
Sistema Ox Bel Ha
270.2 km (167.9 mi)
near Tulum, Quintana Roo, Mexico
1996
southern parts in Sian Ka'an Biosphere Reserve
Shuanghedong Cave Network
257.4 km (159.9 mi)
Guizhou, China
1988
Suiyang Shuanghedong National Geopark
Optymistychna Cave
257.0 km (159.7 mi)
near Korolivka, Ukraine
1966
Dnistrovskyy Canion
Wind Cave
241.6 km (150.1 mi)
near Hot Springs, South Dakota, United States
1881
Wind Cave National Park
Clearwater Cave System
227 km (141.1 mi)
near Miri, Sarawak, Malaysia
1978
Gunung Mulu National Park, also a World Heritage Site
Lechuguilla Cave
222.6 km (138.3 mi)
near Carlsbad, New Mexico, United States
1900
Carlsbad Caverns National Park
Fisher Ridge Cave System
208.8 km (129.7 mi)
near Brownsville, Kentucky, United States
1981
partly within Mammoth Cave National Park
Hölloch
201.9 km (125.5 mi)
Muotathal, Switzerland
1875
none

Question: How long is the Optymistychna Cave compared to other caves in the world?
Answer: Optymistychna Cave is one of the longest cave in the world, after Mammoth Cave, Sistema Sac Actun, Jewel Cave, and Sistema Ox Bel Ha.