Check in was done by Ruslan, and he was very friendly and welcoming!
Location was excellent. Slightly under 10 mins from Karlsplatz station (U1).
Right next to Naschmarkt, 3 min walk around the corner.
4 to 5 minutes to the MuseumsQuartier and around 10 to 12 minute walk from Naturhistorisches Museum Wien (natural history).
Around 15 minute walk to Stephansplatz.
As you can see, it really is in a very convenient location, and yet totally away from the hustle and bustle. Hence a good night sleep everynight.
Side note, do check with them on the toiletries as we did not have Shampoo and shower gel. But just a message to Ruslan and it would be fixed!