Greece is known the world over for its historic sites, sparkling sea, and lovely, vine-shaded restaurants. Add riot police, shuttered banks, and lines at cash machines and the picture clouds.

This is the reality facing tourism in Greece this year, as the peak summer season in the popular destination is threatened by a financial crisis of frightening proportions. Up until now, the charming cafes and outdoor restaurants near the Acropolis have remained overflowing with tourists, but considering the bad publicity of the past week's events, many businesses say they are beginning to see cancellations and a slowdown in reservations.

"Our future bookings are down 20 to 30 percent," said Edward Fisher, who owns and operates Athens Backpackers and Athens Studios, with prime locations near the Acropolis that cater mostly to youthful travelers without mega-budgets.

He blamed the global media for the marked slowdown, and said he believes it will only be a "temporary blip" because of Greece's timeless appeal.

"There's something mystical about Greece," said the Australian who started his business 12 years ago. "It tickles a different sense. (...) So we're not panicking. But I want to avoid a humanitarian crisis here."

Tourism and the foreign funds it generates are vital for Greece's hoped-for recovery from its deeply indebted state. The World Travel and Tourism Council said tourism's direct contribution to the Greek economy was more than 29 billion euros ($32 billion) in 2014, accounting for just over 17 percent of the country's GDP.

As such, the Greek National Tourist Board is taking steps to reassure tourists that their credit cards and bank cards will work normally and that restrictions applied to Greek citizens will not apply to visitors. Lyssandros Tsilidis, president of the Hellenic Association of Travel and Tourist Agencies, maintained an optimistic view, saying tourism figures are holding steady nationwide.

"There are more rumors about cancellations than actual cancellations and reservations are still coming in," he said. "Tourists are having no problems."

Visitors to the famed Acropolis and surrounding areas agreed, telling The Associated Press they had been able to enjoy normal holidays without disruption.

"I have seen a few lines at ATMs but there are no huge lines," said Luciane Souza, a Brazilian lawyer making her first trip to Greece. "I love the place. For having fun, it's no problem."

John Kopari, visiting from Duluth, Minnesota, added the crisis hasn't affected him and his family "one bit."

But for those who haven't yet booked their trips, such assurances are not soothing fears that the ATMs and the banks may soon run out of cash altogether, unless there is an infusion of euros delivered by the European Central Bank or another emergency source.

And some restaurants and hotels have posted signs saying they will not accept credit cards, despite the government's pledges.

Tour guide Christina Poulogiani, exhausted after leading German, Austrian and Swiss tourists to the Acropolis in the hot sun, said Tuesday was the busiest day of the year, but that future bookings are in doubt.

"People are waiting before they commit," she said. "Business is good right now but people are worried because groups are not committing."

The crisis could not have peaked at a worse time from the point of view of the hundreds of thousands of Greeks who depend on income from the frenetic summer months to keep their families going during the slack winter time.

Elman Vasileios, manager of the Majestic Travel agency in central Athens, said the bank shutdown has made it impossible for him to conduct business as usual. To make matters worse, major airlines have emailed his agency in the last day telling him he cannot issue any tickets, even to customers with cash.

"We cannot operate as we used to because we have no quick access to funds if people pay by credit cards," he said. "We also have a huge amount of money stuck in the bank that we can't get access to."

His agency is still accepting credits cards, but it is taking days or weeks for him to be able to get his hands on the money via various electronic bank transfer systems.

He has several overlapping problems: Tourists are shortening or cancelling their trips to Greece, and, a substantial number of Greeks concerned about their own finances (and particularly their supply of cash) have cancelled their own summer holidays, traditionally taken on some of the treasured islands that dot the Mediterranean here.

"Greeks going on holiday this summer have fallen to zero and I mean zero," he said. "I just had a group of 40 cancel. They don't have access to their funds and they don't know when they will. This season has been destroyed. Foreign embassies are warning people about problems so people think twice about coming to Greece."