Roktface at ROKT climbing centre in Brighouse, West Yorkshire, has been built on the side of an old grain silo.
Creators said when it opens in May, amateur and professional climbers will be able to explore routes of up to 36m (118ft).
Team GB climber, Luke Murphy, said setting the routes had been a "real experience".
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"Not many people can say their office is the side of a wall that's higher than the Tower of London," he said.
"Even I found it a bit surreal, but it's been great fun installing the holds and I literally can't wait to properly tackle it when completed."
The Â£75,000 project is a partnership between the climbing centre and Calderdale Council.
The final holds are being installed on what its creators say will be the UK's highest man-made outdoor climbing wall.