This structure was built centuries ago.

The 20th century was marked by significant advancements in science and technology.

What is this thing?

We are planning to build a new house.

We are working hard to build a new system.

We are working on the construction of a new system.

This is an important invention of the 20th century.

It's surprising that he can run so fast.

What? I couldn't catch what you said.

Could you bring me that, whatchamacallit?