Please be aware that in Bulgaria, prices may be quoted in both the local currency (the Lev) and in Euros (€), even though the country is not yet in the Eurozone.
If you book any trip through the hotel, make sure to confirm which currency they are using—better yet, ask for a printed pricing sheet. We booked a tour through a hotel employee who gave us the price over the phone but did not specify the currency. We assumed it was in the local currency, but when it came time to pay after the trip, we were surprised to find they wanted payment in Euros, not Levs.
The hotel itself was very nice and conveniently located near everything.