I just chanced upon a friend's Weibo post that reads:

"我小时候家，大连这样的建筑街景随处可见，现在，只是存在于记忆中！"

accompanied with a picture of, you guessed it, a collection of crumbling shops soon to be 拆ed off.

My question, however, concerns 于. In the above sentence, 于 looks to function as "in"; "when I was a kid you could see this kind of architecture anywhere on the street in Dalian, but now it exists only in memory." Pleco lists 于 as alternately "in", "at", "to", "from", "out of", and "by".

What are some of the most common ways to employ 于 in speech? writing? I've studied more than 18 months and never found reason to learn how to use 于 despite it apparently carrying the strength of every preposition in the English language. Have I blundered, or is 于 rarely found in the wild?