Smederevo Fortress

Impressive 15th Century fortress on the banks of the river Danube. It was once a fortified city and temporarily the capital of Serbia before it was overrun by forces of the Ottoman Empire but not until they had laid siege to the fortress on three separate occasions. 
The fortress survived the centuries more or less intact until bomb damage in World War II. In recent years the fortress has been restored back to it's former glory as has the spectacular fortress a few miles downriver in Golubac.
There isn't much else to detain you in Smederevo, it's an industrial city with a large steelworks that seems to coat everything in a red dust. From memory the nearest places of interest are Belgrade to the north and Veliko Gradiste to the south, both around 40 miles away.

I visited this site few months ago. Amazing medieval castle build by Despot Djuradj Brankovic in the begining of 15th century and its still standing. It was a last defence against Ottoman Turks. When they overrun Serbian army there, medieval Serbia stoped existing and then started a 500 years slavery under Ottomans. This is a reason why is so important site. Its very easy to come here. From Belgrade or any other city. You can see it coming into the city. Free to visit, except towers, but ticket is simbolic(around 100 dinars=less then 1 euro).

Visited the site in August 2011, one of the most spectacular fortresses in this part of Europe. The whole area is currently a park with free access. The only place with limited and fee entrance is a keep (or donjon) which is initial medieval castle (the beginning of a fortress)-nice views from the towers of the site and Danube river.

During my visit I saw a photo exhibition of all Danubian fortresses including Bac, Petrovaradin, Belgrade and Golubac - good idea for serial listing - all are very well preserved and remarkable places (especially Golubac).