For traveling you have many possibilities: one of them are trains and buses, but I do believe that renting a car at the airport is a much more flexible opportunity.
The first destination is Belogradchik. The bus ticket costs 8 euro in each direction.
Belogradchik is a town in the very westnorth part of Bulgaria. Literally translated the name of the town means ‘small white town’. The main activity will be the Belogradchik rocks and the Belogradchik Fortress. The latter is an ancient fortress, one of the best-preserved strongholds in Bulgaria and a cultural monument of national importance. There you will be able to enjoy the incredible beauty and mysticism of the Belogradchik Rocks. They are a group of sandstone and conglomerate rock formations with strange shapes, which have been forming for over a million years. They vary in color, size, as some of them reach up to 200m. There is a lot of historical value and legends, which the native people will be more than happy to share with you.
Most of the hotels in the city have a very nice spa area, which you can make use of after a day spent climbing. The restaurants offer amazing typical Bulgarian food, which you shouldn’t miss either.
Once you have visited Belogradchik you should visit cave ‘Lepenitsa’, just 4 km from Belogradchik. In it were found seven pearls - some of the rarest natural formations that are now exposed in the National Museum of Natural History in Sofia. The number of species inhabiting the cave is about 20, among them are eight species of bats.
Then you will be ready to head to the waterfall ‘Bela Voda’ just 23 km away from Belogradchik. t is a designated landmark and is included in the longest itinerary in the Western Balkans. It will require you a 30 min walk to get to the waterfall, during which you will be able to enjoy the beauty of the north-western Balkan Mountains.
Afterwards, and my personal favorite, comes cave ‘Magura’, which is as well around 25 km away from Belogradchik. The prehistoric wall paintings of Magura have great resemblance with those of the Grotta dei Cervi in Italy, which are of exceptional expression and artistic depth and are considered the most significant works of art of the European Post-Paleolithic era.
Once you have visited those, you must be tired enough to head to Vidin, where you can spend the night. Vidin is the capital of this region and has very important historical value. Hotels are quite reasonably-priced and you can find many Airbnb opportunities, the cuisine is once again a must!
In the last day of your trip, you must be able to visit the Baba Vida Fortress. It is the town’s primary landmark. Many legends surround the monument. During the Ottoman empire it even served as a weapon warehouse and a prison. Nowadays it is a museum, one worth visiting!
Other activities in Vidin can be the historical museum ‘Konaka’ and the neo-Gothic styled Synagogue of the city. These two are very impressive and historically valuable. You can also visit the markets of the city, which offer food produces in the city and the towns surrounding it.
Afterwards you will be ready to return to Sofia, where you can catch your flight.
The bus ticket from Vidin to Sofia is ranging between 8 and 9 euro in a direction.
The best option would be to arrive in the afternoon of Friday/Saturday in Sofia, the capital of Bulgaria. There are many low-cost airlines such as Ryanair and Wizz Air, which land in Sofia, as well as other more customized ones such as Lufthansa and Turkish Airlines.
You will be back in Sofia, Bulgaria at the end of the trip. You will depart from Sofia Airport is the main international airport of Bulgaria, located 10 km east of the centre of the capital Sofia.