Hi URA,
I'd probably say the building of some great structure. Perhaps the Burg Khalifa. The technology to take man into space would also be pretty high up there, but technological advancement is surpassed today so rapidly that it's hard to see just space exploration as being the best of such advancement. Perhaps if one day we do have space travel as commonplace as airplane travel is today, it might supplant my personal idea of the pinnacle of man.
The daily physical presence of the Burg Khalifa is just such an awesome engineering feat. To think that we can build a structure that stretches a 1/2 mile into the sky and it stands, just seems pretty awesome to me. Of course, that's also what brought on God's wrath in the days of Nimrod. God's testimony in that day was that nothing that man puts his hand to shall be impossible for him. So tall buildings just remind me of that claim of God and how man still is trying to build structures to reach up into the heavens.
However, it will fall one day. When God causes the whole earth to shake, I'm fairly confident that all of our grand and mighty structures in which we put so much of our pride, will fall tumbling to the ground.
God bless,
In Christ, ted