It was first thought of in 1956, but the first Commercial flight was in 1976.
It Took about 20 years
26 months
14
14 years
10 years
10 years
The Templo Mayor in Tenochtitlan, which is present-day Mexico City, took approximately 200 years to build. It was continuously expanded and reconstructed by various Aztec emperors until the Spanish conquest in 1521.
28 years
to many years to count
three years
12
10 Years