The old course of the Mikośka was diverted in a 2007 tunneling project
Use native language for Internet searches
Vintage maps of the city of Rzeszów, Poland clearly show a small tributary water course that flows through the old city and empties into the Wislok River. There is little or no trace of that stream on the present-day map of Rzeszów. Clearly it was re-engineered to flow underground in one or more phases since the 1909 map where it appears but without a name.
I wanted to learn more about that—when the project was undertaken and how the changes affected the adjacent buildings and public spaces along the former stream. This is the kind of search we all do every day, but this time I kept coming up blank, using every combination of the terms Rzeszów river/stream underground/culvert/tunnel. Without a name for the stream, I could find nothing about when and how it was reengineered.
Finally, I gave it one last try with my search term translated into Polish. I fired up Google Translate to find that "underground river" is "rzeka pod ziemią." I added Rzeszów to that and entered a Google Search.
Boom. Right away I learned that the name of the stream was Mikośka and that, yes, it had been diverted through a huge underground pipe sometime after 2007. Here is a translated Polish news article about it. The images show an early illustration and a map of the diversion project.
The moral is that you can save yourself a lot of time and frustration by thinking to do Internet searches using search terms translated into the local language. Yes, the search results will also be in the native language, but those links can be easily back-translated. You don't have to know a word of the other language to perform quicker, more efficient Internet searches.