It served as the primary stronghold in the capital of the Second Bulgarian empire. It’s situated on the Yantra river, on a hill of the same name, across it is the other main hill in the medieval city - Trapezitsa.

It was conquered on 17 July 1393 by the ottomans after a three month siege, during which the tsar was at Nikopol, leaving the Bulgarian patriarch to defend the city.

On 22 September 1908, at the foot of Tsarevets, in the Holy Forty martyrs church, tsar Ferdinand declares Bulgaria’s independence from the Ottoman Empire.

Here’s a great guide for Tsarevets