The Citadel of Soimos was built after the first invasion of the Tatars and documented since 1278. Soimos Citadel is on the list of historical monuments.
From 1278 until 1509, the city was ruled by Ladislau Kan II and Iancu of Hunedoara.
In 1509 the citadel and the domain become the property of Gheorghe Hohenzollern of Brandenburg. It was besieged in 1514 by Romanian and Hungarian rebels, led by Gheorghe Doja. After a brief resistance, the garrison of citadel led by Prince of Ciuci is an uprising against people of Gheorghe Hohenzollern and joins the rebels.
Turks occupied the citadel in 1552, after repeated sieges, and in 1595 was recaptured by György Borbély - Captain of Stephen Bathory - reaching into custody rulers of Transylvania.
In 1599-1600 pass under the rule of Michael the Brave (Mihai Viteazul). The citadel was finally liberated from Turkish domination in 1688.
http://www.uvisitromania.com/tourist-attractions/arad/soimos-citadel-id535