Completing the 32-day journey was an overwhelming experience, Mr Caldwell said.
"What was really nice in the last stages, was that three Invercargill cyclists joined me."
The other cyclists helped shelter him from the wind until they neared Sterling Point, he said.
"For the last kilometre I just rode it on my own. It was a fantastic feeling - it was indescribable, really.
"It was unquestionably one of the best things I've done. While I was doing it, it seemed very normal but since I've been back I feel like a different person ... when you do something that's completely unrelated or different to your everyday life, you are putting your mind and body into a different zone."
Mr Caldwell, who was diagnosed with type 2 diabetes about 10 years ago, cycled between 80km to 150km a day, and completed the journey two days ahead of schedule.
He was accompanied by a support van provided by Eastwood Motor Group.
Mr Caldwell's Roubaix Elite carbon-fibre road bike, nicknamed " Awesome Amy," was donated by Penny and Todd Hart of Carterton.
The trip has so far raised about $4000 for Diabetes Wairarapa.
Donations are still open at http://www.diabeteswairarapa.org.nz/