u/FR-DE-ES

Just like this time last year, half a dozen "Pozor Žáby" signs appeared on lamp posts on the paved foot path from Petřínské terasy restaurant continue through Promenáda Raoula Wallenberga towards Strahovský klášter. I walk this route twice a week in the afternoon at this time of year for the 4th consecutive year and never heard/saw a frog. This sign is a mystery to me.

Could those in the know tell me why this warning is necessary at this time of year? Why this particular stretch of the foot path but not the countless other foot paths on Petřín?

I need to buy brooms to sweep dirt & dry food crumps off parquet living room floor & stone kitchen floor. Which stores have large selection of brooms to choose from? Suggestions greatly appreciated.

I am very much affected by air quality (pollens / pollution / dust). Is there a reliable web site/app that measures Prague's air quality in real time?