Mountain biker Melvin Ee, 44, used to be limited to a 1.6km trail at Chestnut Nature Park, next to the Central Catchment Nature Reserve.
With the official opening of the northern section of the park yesterday, the mountain bike trail is now 8.2km.
Chestnut Nature Park has expanded from 17ha to 81ha - equivalent to more than 110 football fields - making it the largest nature park in Singapore.
Besides the longer mountain biking trail, the hiking trail is now 5.6km, up from 2.1km.
National Parks Board (NParks) classifies most sections of the biking trail as moderately difficult to extremely difficult. "They're less technical than the ones at Bukit Timah Nature Reserve," said Dr Ee.
Chestnut is the only park with separate trails for bikers and hikers. It also has Singapore's first pump track for stunt bikers.
Senior Minister of State for Home Affairs and National Development Desmond Lee officiated the opening yesterday.
He said the park is one of five buffer parks to protect the Central Catchment Nature Reserve from urbanisation impact. Two more parks, Windsor and Thomson, will be opened in future.