But it has been beset by technical problems since its launch at the Staffordshire park in May 2013.
On June 2, 2015, a loaded train collided with an empty test train, causing serious injuries to a number of riders.
Two teenagers - Vicky Balch and Leah Washington - needed their legs amputating after the crash.
Leah's boyfriend Joe Pugh's knees were shattered by the blow while Vicky's boyfriend Daniel Thorpe suffered a broken leg and punctured lung in the horror.
Alton Towers owner Merlin Attractions Operations Ltd was prosecuted in April 2016 and later fined £5million ($8.8 million) for health and safety breaches.
Earlier this month, the rollercoaster was evacuated after a rider triggered an alarm on a safety harness.
One rider claimed to have been "hung upside-down for an eternity" as the Smiler ride stopped.
@t0wen said on Twitter: "I was on there. 45 mins. Not cool."
Responding to someone who asked what happened, he added: "God knows. Ride malfunctioned and we all hung upside down for an eternity."
Eugene Prokudin took several videos of the technical fault from the queue at Alton Towers, Staffs.
Referring to the carriage that was stuck on a vertical climb, he said: "And that's what you don't want to happen with your cart when you're stuck at 90 degrees.."
Aimee King was about to queue and decided against using the ride.
She said: "Smiler breaking down just before we were about to queue*no thanks."
Several other Twitter users have claimed they too were stuck on the ride in the past month.
Posts from May 30, June 17 and June 18 all claim the ride had stopped half way through.
An Alton Towers spokeswoman said yesterday's issue was a minor technical fault and the ride had done exactly what it was supposed to do and stopped.
She said: "At 16.26 yesterday The Smiler experienced a temporary stoppage as a result of a sensor detecting a minor technical issue.
"This was completely normal and what the ride, as well as others, are designed to do at theme parks across the world. At no point was guest safety compromised."
