Köln Dom, St. Paul's, Machu Picchu, any of the temples in Angkor, NY Grand Central Station, Milan main station, Neuschwanstein Castle, most of Rome.
Can't say any modern stuff that gets modelled on computer then thrown up in a few months by cranes interests me at all.....it's the effort that went into it that makes the best and most impressive buildings.
Most of Rome...can't fault that.
Define effort. Physical effort, brain power, using tried and tested techniques or pushing the boundaries of todays technology?
Whilst I respect your view, I am sure its a different sort of effort is used to build modern buildings today. The tolerances, exactness and economy of materials compared to the way older buildings were built are all very different.
I'll finish with this image, it tells a story.
_DSC2135 by
SFTPhotography, on Flickr
The front bridge is the original forth crossing, now 125 plus years old. It would have involved the most people in building, the most raw materials etc. The next bridge along is the Forth Road bridge, went up in the 60's, behind it, you can see the building of the new Forth Road bridge as the construction of the 1st road bridge wasn't really upto scratch. All of them mark their place in time, and all are interesting as they reflect the era in time of which the come from.
Effort wise, the newest one has maybe taken the least, but it will be the most advanced one, and in terms of precision and exactness may represent the biggest technological effort. It's gone up and will be ready in 2016, thats an incredibly short time frame.