[grania]

It’s humbling, isn’t it? Thousands of years ago dams, roads and buildings were constructed that still stand, some still in use. Modern technology has trouble constructing anything that lasts more than fifty years.

[Eric in the Ozarks]

Bagnel Dam here at Lake of the Ozarks was built in 1930.

[SunkenCiv]

Yes indeed.

http://en.wikipedia.org/wiki/File:Roman_Cornalvo_dam,_Extremadura,_Spain._Pic_01.jpg

https://www.google.com/search?q=proserpina+dam&espv=2&biw=1366&bih=600&tbm=isch&tbo=u&source=univ&sa=X&ei=z4L0VPr_JsSeyASbroG4Dw&ved=0CCoQsAQ&dpr=1

And Sri Lankans built 12,000 dams:

http://www.mysrilankaholidays.com/ancient-sinhalese-irrigation.html