NARACOORTE Caves had a particularly busy December, with the world heritage listed site breaking a 10-year record.
Visitor numbers for the month were the highest they had been since 2003 with 7415 tourists stopping in, more than 300 up on last year.
Almost half of the visitors over the 31 days came from Adelaide, Melbourne or overseas.
Park manager Deborah Carden said it was a trend she'd seen in previous times and over the past 12 months.
"It's really interesting," she said. "I think Christmas falling on a Wednesday instead of a weekend was a factor...it makes the holiday period longer for most people.
"This year it will most likely be the same because Christmas is on a Thursday."
So far January has also seen high visitation numbers - figures from January 1 to 19 already show an increase of 1222 people from the same time last year.
A report based on visitor postcodes determining where people are coming from revealed all but two groups - ACT and regional Queensland - were up from 2013.
Most people had come from parts of SA, Victoria and overseas.
Ms Carden said she thought consumer confidence, due to a stable Government, and an increased exchange rate contributed to the cave's busy holiday period, as well as marketing strategies.
"On the website we have the program for summer up," she said.
"We're finding people have already researched what they want to do before they even come to the caves.
"The visitor information centres around the region are also very supportive and help a lot."
Last week's heatwave wasn't a deterrent either.
"The most severe day we dropped back a bit but the next day we were markedly up," Ms Carden said.
"It's very nice and cool in the caves anyway."
Senior guide Decima McTernan added the new town entrances, featuring a diprotodon sculpture, also piqued interest.
"They're capturing people going through (Naracoorte)...people don't necessarily just flit through any more, they investigate and seek to find out more," she said.
"There has been a lot (of people) wanting to see the Victoria Fossil Cave and we've had big numbers on the Alexandra Cave.
"At night time the bat tours are really popular."
Naracoorte Caves will continue its voucher promotion this year, encouraging tourists and locals to check out the caves by placing booklets in local businesses.
"It has been really good for us and the town," Ms Carden said. "It makes locals realise it is their park and that it is in their back garden."
Mrs McTernan agreed: "It's about community ownership. We are certainly getting vouchers in every single day."