The city of Kassel was initially skeptical. Would the  contemporary art exhibition staged in the city once every five years do well this time, with Kassel sharing the 2017 edition with the Greek capital, Athens?

It turned out their worries were unfounded, and even more people have been flocking to see artworks from all over the world than came to previous editions.

About 445,000 people have visited the exhibition so far, 17 percent more than at the same time five years ago, organizers say. In 2012, the art show recorded a total of 905,000 visitors by the end of its 100-day run.

Read more: Art for Athens: what Documenta left behind

The outdoor artworks set up in parks and city squares draw crowds in particular - and they are free. Marta Minujin's huge "Parthenon of Books" is a favorite on the city's central Friederichsplatz Square. On July 29, the exhibition's half-way mark, people will publicly read aloud all night from the once-forbidden books.

The steel scaffolding, in shape and size an exact replica of the Acropolis in Athens, is covered in more than 50,000 plastic-wrapped books. The artwork is designed to remind people of censorship and persecution of writers.

Even weeks after the exhibition opened, the artwork is not finished. Eight columns are still empty, waiting to be draped in forbidden books. The much-visited attraction is only cordoned off to visitors during thunder storms.

Smoke from the tower

The artworks are holding up well despite the rainy weather over the past days, says Joachim Gries from the Kassel Fire Department. All the same, their emergency number is often busy as people continue to call in a fire when they see smoke rising over the city from yet another artwork, not far from the Parthenon installation.

"We know how to deal with the situation, and we're recording fewer calls than at the beginning," Joachim Gries says, adding that more than 600 emergency calls have come in so far because of the smoke billowing from Daniel Knorr's "Expiration Movement" art installation on the Zwehrenturm tower.

When the smoke goes straight up into the sky like from a chimneystack, it is meant to symbolize the art market as an industry, according to the artist. The fire department has meanwhile installed a lookout on site to keep an eye on things.

Discover horizontal life

The stack of pipelines by Iraqi artist Hiwa K - they look like sewer pipes - near the Parthenon of Books are one of the exhibition's highlights. Many visitors wonder whether they are inhabited, and some do look inviting as 13 students from the local university furnished the 20 pipes in cooperation with the artist.

Documenta art exhibition more political than ever

Each student furnished one pipe, says Jennifer Witulla, who outfitted a pipe with a small kitchen and a sleeping accommodation. "I tried to make it comfortable, but all you have is a space that has a diameter of no more than 900 millimeters, so many objects had to be multifunctional."

Hiwa K, himself a refugee, says he saw people spend the night in similar pipes. He told the students who participated in the project that he does not see the refugees as victims, however.

"He wanted to turn his own experience into something positive," Jennifer says, adding that the fact that the pipes are horizontal highlights the vertical aspects of our society - above all, the capitalist society.

The horizontal pipes are designed to give people a "horizontal attitude to life; he feels that is important," Jennifer Witulla says. And it is an injtersting experience, she adds. "You experience your body in a different way; you have to move differently - that's what makes it interesting."

New approach

The documenta contemporary art exhibition expects people to throw their preconceptions of art overboard and take a fresh view. That is part of the concept devised by artistic director Adam Szymcyk - which may not be everyone's cup of tea.

All the same, the mood is good. More than 11,000 people have bought season tickets, which shows how popular the exhibition is with locals, too.

Meanwhile, the city of Kassel is presumably eying one or more of the artworks with the intention to buy, as it usually does. The highly popular over-16-meter-tall obelisk by Nigerian-born US artist Olu Oguibe, a monument dedicated to refugees set up in the heart of Kassel, might be a hot contender.