Mount Mulu
The earliest reference to the Mulu caves was in 1858 when Spenser St. John (British Consul in Brunei) mentioned the "detached masses of limestone, much water-worn, with caverns and natural tunnels” in his book "Life in the Forests of the Far East". Spenser tried to ascend Mount Mulu later but failed due to limestone cliffs, dense forests, and sharp pinnacles.