

A look at the fate of United Airlines Flight 232 which crashed into Sioux City's runway in 1989; it caused a subsequent explosion that left 111 people dead.

Seeing how international investigative teams must overcome differences to solve controversial plane crashes.

Visiting Australia's One Central Park, the Oslo Opera House and the California Academy of Sciences in San Francisco to reveal their architectural secrets.

Engineers grapple with an apartment building, ripped apart by a man-made canyon; the Gateway Arch takes shape in St. Louis; an unpromising plot in Copenhagen, Denmark, is transformed by a gleaming new triangular office.

A museum building bends 1,100-glass tubes to form a facade and tunnels below the water table; a vast 11-storey glass atrium HQ is built on the former Berlin Wall site to represent unity.

Lord Foster's five-winged steel towers cool Abu Dhabi's national museum naturally. Robots 3D-print a steel bridge in Amsterdam & a concrete tower in Switzerland. And in Sydney, engineers pump out the harbour to build a fish market.

NASA's 3D-printed Mars habitat rehearses human life on the red planet. Seoul's historic city hall gains a 13-story glass wave. And in Dallas, 68,000 square feet of concrete galleries balance on legs that want to splay open under.

Building an eco-friendly visitor center in the permafrost on Colorado's Pikes Peak tests the team. A museum is constructed in a disused dry dock that's in danger of collapse.