St. Johannes Nepomuk Kapelle is a small Otto Wagner chapel in Alsergrund, designed between 1893 and 1897. It is an early religious work by the architect, and you can already see ideas that would later become much grander at the Kirche am Steinhof.
This is a quick architectural stop rather than a destination for everyone. It is best for visitors already tracing Vienna's Jugendstil buildings or exploring the quieter streets north of the centre.