The National Park Service as a part of the US Department of Interior operates the National Register of Historic Places which now includes over 80,000 listings.
Monastery: Rila, Vachkovo. Balchik- place and bot. garden. King's residence in Vrania, Old town of Nessebar (in UNESCO list), Alexander Nevsky church at Sofia, Batak- ruins from Otoman Empire, Osman...