building infrastructures upon roof tops? Collapsible, Mobile? Shipping containers?

Excavator on roof top of 12 story building in Taiyuan

The design studio Playze stacked up shipping containers to create a building for an organic farm in Shanghai, China

Shipping Containers used to create a pop-up Mexican Wahaca restaurant on London's Southbank.
Where diners even receive their own chilli peppers to grow at home.
First opening during the London Design Festival. Mobile?

Tree houses? Building houses? Buildings upon buildings? Towers

Shipping container architecture has been becoming increasingly popular, it is a fairy low budget easy way of constructing a space with many ready available. But what else could you use as an alternative?

Garden sheds? Greenhouses? Caravans? Tents? Something temporary?