The popular Pulpit Rock lookout in the Blue Mountains was scorched in the Black Summer bushfire.
Visitors will pay $12 an hour to park at the site.
Neil Monteith was hanging off the side of a 100-metre sandstone cliff face in the Blue Mountains when he saw a giant plume of smoke gathering across the valley.
"This large mushroom cloud started to form over on the other side."
The Black Summer mega fire swallowed the Grose Valley and leapt up the cliff, destroying the Pulpit Rock lookout.
"All the wooden steps that led down to the lookout were totally erased," Mr Monteith said, recalling that piles of metal and wood were all that was left of the timber shelters that formed the picnic area.
Blue Mountains Mayor Mark Greenhill worked as a firefighter during the Black Summer, and he remembered what Pulpit Rock looked like in the wake of the fire.
The work was funded with almost $1 million from the Commonwealth and $3.7m from the NSW government.
Cr Greenhill said the six-year closure was due to the "complex' nature of the restoration work."
Cr Greenhill said the council's geotechnical investigations found the lowest lookout could not safely be rebuilt, but the three others had all been upgraded.
The Blue Mountains City Council has installed paid parking meters at the lookout, which Mr Monteith said could cause climbers and hikers to think twice about visiting the area.