That is a matter of opinion.
Eugene Ely was a pilot who piloted a Curtiss biplane on the first flight to take off from a ship. Also asphalt was being manufactured from oil refining byproducts.
Feat is not a verb. Feat is a noun, as in, "He has accomplished a great feat by winning a gold medal in the Olympics." A synonym of feat is achievement.
Yes. It is an amazing feat of engineering.
hoover dam
The reason why it was such a magnificent engineering feat is because of the elevations, the Yellow Fever, the challenge of managing a flooded river and the differences in tides.
passing my exams was a great feat
They Build Stone Houses.
A feat is an act of great strength or skill. A feat might also be an act of daring performed in front of an audience.
The closest I can come to an antonym of feat is triviality. A feat is a notable accomplishment (such as a feat of strength) so an accomplishment that is in no way notable could be described as a triviality.
panama canal
Sir Edmund Hillary is credited with being the first man to climb Mt Everest in the Himalayas.
There are many, the Aqueduct, the Coliseum, the Pantheon, Sewers, the Roman Baths.... among hundreds of other fantastic architectural and engineering marvels.