SOFIA -- In 2012, Dutch-Canadian photographer Paolo Woods was living in Haiti when friend and fellow photographer Gabriele Galimberti came to visit. The subject of taxes came up and Galimberti, an Italian national, mentioned that his tax bill had arrived and that Rome was about to claim nearly 50 percent of his income.

The pair joked that with the Cayman Islands just a short distance away, Galimberti should "just go and hide" his money there.

The photographers then realized they knew almost nothing about the murky world of offshore banking. Two months later, the pair flew to the Cayman Islands to begin work on a project that became known as The Heavens.

The photo project is being exhibited in Sofia's Synthesis gallery until June 15 and offers a fascinating glimpse into the virtually invisible world of offshore tax havens.

"This whole system is secret," Woods told RFE/RL's Bulgarian Service. "As a journalist, when you want to investigate it, it does everything it can to stop you.

"Gabriele and I realized that the offshore system is closely connected to the global economy and that much of this system is actually legal."

From the U.S. state of Delaware to the Virgin Islands, offshore zones serve as places to invest wealth anonymously and avoid tax obligations.

As well as offering a place to park money and assets, offshore territories also enable people to set up opaque legal entities. Such "shell companies" can have their own assets of artwork, cash, and real estate ownership.

Secrecy is at the core of the offshore banking system, and getting permission to enter was by far the biggest challenge of the photo project.

"It was extremely difficult," Woods says. "It took a long time to put the project together because it's almost impossible to get access to these places and institutions. Many of them turned us down, and some blocked access as soon as we arrived."

As an illustration of the levels of secrecy and security of this financial underworld, the photojournalist says some of the offshore facilities include storehouses accessed through multiple doors that required codes and iris scans, meaning an insider was required to be with them every step of the way.

The photographers say their project aims to raise moral questions about the issue of tax havens.

Some $32 trillion is estimated to be held in offshore entities around the world. Much of this wealth is owned by super-rich individuals, but an increasing share belongs to companies that use the havens to escape regulations or tax obligations -- in many cases perfectly legally.

Wood calls such havens a "structural instrument of the globalized economy."

The impact that storing wealth out of reach of governments can have is not immediately obvious in the same way other global issues are, the photographers say. But the loss of tax income for health care, education, and infrastructure has a very real impact on the world.

"When you see a picture of a child dying in war, you understand how cruel it is," Woods told RFE/RL's Bulgarian Service. "It's hard for many people to understand the consequences of offshore zones because they can't see them with their own eyes."