Ai Weiwei knows what it means to be a refugee. He was persecuted in his homeland China. His fall 2017 show in New York deals with the global refugee crisis through artwork distributed over the city's five boroughs. One of the largest of his installations, entitled "Gilded Cage," is located on the edge of Central Park (above). It invites viewers to enter and exit it by passing through turnstiles.

His largest work to date, "Law of the Journey," is a 70-meter-long inflatable boat with 258 faceless refugee figures that was shown in Prague. Ever since he moved to Berlin in 2015, Ai Weiwei has worked on numerous projects related to the plight of refugees, often meeting them personally. His documentary "Human Flow" was up for the Golden Lion Best Film award at the 2017 Venice Film Festival.

In late 2015 the image of 3-year-old Syrian refugee Alan Kurdi washed up lifeless on a beach made headlines around the world. In January 2016, Indian news magazine India Today published the above image of Ai Weiwei on the Greek island of Lesbos. While some praised the image as artistic activism, not everyone found the visual protest against European refugee politics ethically acceptable.

The exhibition "Luther and the avant-garde" features contemporary art. According to the 16th century religious reformer himself, images are neither good nor bad; they can inspire belief and prompt contemplation of God. Martin Luther's perspective on artistic freedom paved the way for modern art. Above, Ai Weiwei displays his take on individuality, religion and resistance in the exhibition.

In 2015, Lego refused to deliver Ai Weiwei a bulk order of the toys on political grounds. Supporters around the world sent millions of pieces in protest. Ai had already used Legos for a work of art on freedom of expression, shown in the abandoned prison of Alcatraz. It featured over 175 portraits of political activists and prisoners of conscience, such as Edward Snowden and Nelson Mandela.

During the 2015 Berlinale film festival, Ai Weiwei directed a movie which depicts his long-distance relationship with his six-year-old son, Ai Lao, who lives with his mother in Berlin. He delivered his instructions for the short film using satellites and via Skype, a logistical tour de force.

Ai Weiwei was allowed to hold a solo exhibition in Beijing in June 2015: This was seen as a sign that the government was easing on his case. Although he avoided direct political works in the show, the authorities pushed back its opening date by a week, as they did not want it to be accessible to the public before June 4 — the anniversary of the 1989 Tiananmen Square Massacre.

This is part of another famous work which counts millions of pieces. These sunflower seeds are deceptively realistic, yet they were all handcrafted in porcelain by hundreds of artisans. The installation comments on the current "Made in China" economy and also refers to Mao Zedong’s brutal Cultural Revolution (1966—76), where sunflowers were typically used in propaganda images.

There are different versions of this installation, "Circle of Animals/Zodiac Heads," which features 12 animal heads reproducing the traditional Chinese zodiac once part of a fountain clock at the Old Summer Palace in Beijing. The sculptures were looted after French and British troops destroyed the imperial retreat in 1850. In June 2015, a bronze version of the work was sold for 3.4 million pounds.

In 2014, Ai Weiwei held a huge solo exhibition in Berlin, which he also managed without leaving China. These 6,000 wooden stools filling the atrium of the Martin-Gropius Bau museum, collected throughout the countryside of his Homeland, did make the trip. Wooden stools have been used for centuries in households, and the artist sees them as a symbol of the disappearing traditions of rural China.

Private car ownership is growing exponentially in China, while the bike fleet is declining. Cyclists are being blamed for causing accidents and congestion. This work is made of 150 bicycles and also commemorates Yang Jia, a Beijing resident arrested for riding an unlicensed bicycle. During his detention he was assaulted and accused of murdering six police officers, leading him to a death sentence.

Ai Weiwei constantly posts pictures of himself on the Internet, such as this one. Air pollution is a major source of protest in China. Social media has become an integral part of the artist's work, allowing him to reach a very wide audience and establish his reputation as a dissident — inspiring many others. He was the recipient of Amnesty International's 2015 Ambassador of Conscience Award.

This laundromat-styled installation features some 2,046 pieces of clothing hanging on 40 clothing racks, freshly cleaned and sorted. The pieces were left behind by refugees in 2016 when the so-called Balkan entry route into Europe was sealed off. Ai Weiwei gathered the clothes and gave them their current appearance, simultaneously giving recognition to their owners' perilous experiences.

The artist also focused on human suffering of migrants in this series of porcelain plates. Made in Jingdezhen, the center of Chinese porcelain ware, the plates' decoration at first appears quite traditional. But in fact Ai Weiwei used his own photos and others found online that documented migration as the basis for the designs. The plates depict war, ruin, sea travel and refugee camps.

The wallpaper pays stylistic tribute to Odysseus, the protagonist in Homer's epic poem who spent years far from home. But the motives actually depict flight and migration. In front stands a marble camera symbolizing state surveillance, a recurring theme of the artist. In 2011, he was arrested in Beijing and detained for 81 days and then kept under government surveillance for more than 20 years.

Ai Weiwei's Odyssey wall also includes numerous photos from a series. The photographs show cultural or governmental landmarks, with the artist holding up his middle finger before each one. The juxtaposition can be seen as a rejection of and protest against powerful political and social decision-makers.

These photos from locations in China are the only black-and-white ones in the series. They show Tiananmen Square, the site of the 1989 repression of students by the Chinese government, on the left, and the Hong Kong harbor on the right. With this year being the 30th anniversary of the Tiananmen protests and many in Hong Kong today fearing greater Chinese control, the works are strongly resonant.

This installation consists of six iron boxes that show scenes from Ai Weiwei's 81-day incarceration in 2011. Viewers can look though small openings to see the scenes that feature the artist and guards. It's a realistic portrayal of the human rights abuse he experienced. Above, a guard oversees the toilet entrance.

This work is another indictment of authority. A total of 142 coffin-like transport boxes made of reinforced steel hold straight steel rods that have been cleaned with cement. With this work, Ai Weiwei remembers the 70,000 people who died in the Sichuan earthquake in 2008. More than 5,000 children alone died in schools that collapsed because corrupt local politicians had cut building costs.

The 12 images in this series are made up of Lego pieces, which is why they look pixelated. The animal heads call forth a vision of eternal cycles and predestined destiny. In the background of the zodiac signs, Ai Weiwei shows representative buildings from his series "Study of Perspective," thus merging two series.

Millions of porcelain sunflower seeds were individually made by 1,600 artisans over two years in the Chinese porcelain capital Jingdezhen. The artwork has a deep political association: Chairman Mao Zedong was often portrayed as the "Sun," and the people were his seeds. In another more present-oriented interpretation, the installation also refers to Chinese mass-produced goods.

A video on the manufacturing process of the 100 million sunflower seeds is displayed in front of a billfold wallpaper. After his detention, Ai had to pay an alleged tax debt of €1.7 million. People sent him money, and he designed 13,719 IOU notes symbolizing their contributions. Ai Weiwei's largest European exhibition to date runs through September 1 at the Kunstsammlung Nordrhein-Westfalen.