ul. "Vitoshko lale" 18
The hotel is brand new and will not show in google maps. We have had the location double checked with the hotel staff though.
You can also see it on booking.com here: https://www.booking.com/hotel/bg/bon-bon-park-amp-spa-boyana.en-gb.html#map_opened-b_tt_holder_3
When you are driving towards Boyana on Blvd. Bulgaria coming from the center, pass under the ring road and take a right turn after that. The hotel is situated a little down that street on the left.