As of 2009[needs update] it is in the midst of extensive restoration and conservation work, despite which the fortress remains "one of the rare preserved courts of medieval Serbian rulers.

[4] This location allowed the Serbian capital to remain near the Christian Kingdom of Hungary, while also satisfying Sultan Murad II of the Ottoman Empire by eliminating the uncontrolled passage of the Hungarians into the Morava Valley.

[6] The fortress' position connecting the Balkans and Central Europe has made it an important religious and commercial center for centuries,[4] now aided by being on the Pan-European X Corridor.

[7] The Danube also connects it to many other historic sites, most notably Belgrade and its suburb of Vinča, Novi Sad, Golubac Fortress, Lepenski Vir and Viminacium.

It also allowed the control of Danube traffic, including blocking Hungarian entry into the Morava valley, which satisfied the Turks.

This marriage stressed the friendly relations the Despot had with the Ottoman Porte, although Ulrich's kinship with the Queen of Hungary implied an increased Serbo-Hungarian alliance.

It stated that Serbia's safety from the Ottoman Empire could only be guaranteed through the marriage of Branković's older daughter to Sultan Murad II.

[6] On August 14, 1435, a formal contract of "brotherhood and friendship" between Serbia and the Republic of Venice was signed in Smederevo's audience hall.

[14][15] In 1453, Sultan Mehmed II and Isak-bey Arbanazović led another attack on Smederevo as part of a devastating raid on Serbia.

That same year, Smederevo was captured by the Ottomans, leading to the end of the medieval Serbian state while Stephen Tomašević fled to Bosnia.

Much of the southern wall of the fortress was destroyed, the nearby railway station, packed with people, was blown away, and most of the buildings in the city were turned into debris.

[4][7] Smederevo Fortress has been described as "one of the most striking and monumental pieces of architecture surviving from medieval Serbia",[4] and "the witness of Serbian creative force.

"[5] It is an accurate display of traditional medieval defensive architecture and has remained well preserved, suffering no major deterioration until World War II.

The fortress and surrounding area have accumulated evidence of the civilizations that developed throughout history, mainly between the 15th and 20th centuries, providing a direct testimony for the progress of the medieval Serbian state and corresponding Orthodox Church.

During construction, Branković's wife Jerina was seen speaking with the foreign overseers—her brother George Palaiologos Kantakouzenos and his men—which resulted in her being commonly associated with the project.

Shortly after it was built, the city reached its peak importance as a religious, commercial, and trade center, at which point it was populated mainly by Serbs and colonies of merchants, primarily from Dubrovnik.

High in the stone wall on the Danube side, four sets of double-arched windows are carved in a combination of Gothic and Romanesque styles.

It reads "V Hrista Boga blagoverni despot Đurđ, gospodin Srbljem i Pomorju Ze(t)skomu; povelenijem jego sazida se grad sij v leto 6938."

The work on the first part, a fortified manor for Despot Đurađ Branković built at the confluence of the rivers, began in the autumn of 1428.

Under the eye of George Palaiologos Kantakouzenos, older brother of Despotina Jerina Branković, lumber, lime, and enormous stones from the former Roman cities of Mons Aureus (the modern village of Seone, west of Smederevo[22][23]), Margum (at the mouth of the Great Morava[24]), and Viminacium were collected.

[4][7] Between 1460 and 1480, while held by the Ottoman Empire, a larger defensive system was built,[4] including escarpments, low walls, and more towers.

[4] The state of deterioration of the fortress ranges widely, from krstata kula which is still well preserved,[18] to sections of the walls which have seen no repair work and have collapsed in some places.

On June 5, 1941, ammunition stored in the fortress exploded,[4][7][18] destroying not only a large part of the southern wall, but also decimating most of Smederevo.

[4][7][18] A dam in the Iron Gate, completed in 1972, raised the water level of the lower Danube basin and caused significant flooding.

Between 1970 and 1980, a system was built to protect the fortress and surrounding city from future high water,[4] however there was once again major flooding in 2006, a result of heavy rainfall and melting snow.

[4][7] The planned final result of the work is for full rehabilitation of both Smederevo Fortress and its immediate surroundings, including relocating the railroad, though estimations of cost vary widely.

The higher groundwater level resulting from the dam in the Iron Gate threatens its stability, and has increased the number of floods, especially before the coast was consolidated.

Unrestricted visits by tourists, combined with inadequate protection, maintenance, and support, both administrative and financial, also contribute to the slow deterioration of the fortress.