While Larnach Castle's profits were down 70 per cent since March last year, domestic visits in December were up 100% on the corresponding time in 2019.
More than 60 per cent of visitors were from the North Island.
"Our gate sales were only down 38 per cent over the holidays because Kiwis made up for other visitors that would normally come.
"We are happy to see that, but you can still see the impact of no international visitors."
While Larnach Castle was cautious about the future, it hoped campaigns similar to Plan D would continue, Price said.
Olveston Historic Home manager Jan Davies said she had appreciated the campaign.
"It was a campaign that caught your eye."
While she could not make a direct link between visitation numbers and the Plan D campaign, visitors to the historic home had been steady throughout the holiday period.
"We marketed throughout the country and we saw the results of that over Christmas. It doesn't compare to when borders are open, but we certainly were supported by people."
Many visitors were from Auckland, but others came from across the country, she said.
"We've certainly had visits from the national market.
"It's been steady but wouldn't cover what we would have if borders had been open."
Enterprise Dunedin city marketing manager Malcolm Anderson said while a final summary of the campaign was not available yet, it received good feedback from local tourism businesses which received visitors as a result of the campaign.
"Referrals to local tourism operators from the DunedinNZ website reached 48 per cent."
Anderson said the initial phase of the campaign was about awareness of Dunedin's offering as a domestic visitor destination, and based on initial research results, media coverage, social media and website engagement, results appeared "favourable".
More specific data was expected to be available by June.
Enterprise Dunedin was working through a refresh of the campaign to encourage more New Zealanders to visit Dunedin.
"Work is also in progress to prepare for when borders to Australia open."
Central government support was also driving the development of some projects which would add to Dunedin's tourism offering, he said.