Giant trampolines have been installed over a chasm inside an old slate quarry cavern twice the size of St Paul’s Cathedral in Blaenau Ffestiniog, Wales.

The new visitor attraction ‘Bounce Below’ will open in July and is the first of its kind worldwide, tipped to lure thousands of daredevil tourists to the region.

The atmospheric slate caverns will be dramatically illuminated while visitors bounce on the three giant trampolines – one above the other linked by a 60ft (18.2m) long slide. Visitors to the underground attraction will travel via train and will then be able to explore the cavern via slide and trampoline.

The £1.2m (US$2m, €1.5m) investment into the quarry at Llechwedd also includes Zip World – said to be the largest zip line course anywhere in the world, which travels up to speed of 70mph (112kmph) and offers aerial views of Snowdonia from 500ft (152m) in the air.

The new development will create 10 jobs with roles for train drivers and instructors, and there are further plans for a series of underground zip lines at the former quarry.