The apartment has an excelent position near Hauptbahnhof and the U1 U-Bahn line.
It was very clean, spacious and with plenty of sleeping and eating room.
Communication with Jay was excellent, giving us detailed instructions and a list of things to visit and recommended restaurants and coffee houses.
A small tip for using the public transport - it's cheaper to get a period pass for the U-Bahn than tickets for every tip and everything can be done via the Wiener Linien mobile app.