Unlike other medieval military fortifications it was not torn down after it lost its primary use. Alexandrov Kremlin is second largest medieval fortification in Russia. Kremlin with its towers and walls defended the original settlement. Its main central building is a Trinity Cathedral. It was built in 1513 and combines Russian medieval and Italian architecture. Alexandrov Trinity Cathedral is covered by frescoes that date to the 16th century. Large copper gates that stand at the entrance of this Eastern Orthodox Church date back to the 14th century. They were taken from another cathedral (either Tver or Novgorod) after raid of Moscow tsar Ivan the Terrible.

The complex of buildings of the Alexandrov Kremlin is designated as the State Historical and Architectural Museum Reserve "Alexander Sloboda". Historical center of Alexandrov is dominated by Crucifixion bell tower that was erected in the 16th century. Small living quarters next to the tower served as a house of future Russian Empress Elizabeth during her exile.

Orthodox Church of the Assumption dates back to the 16th century. Church basement contains medieval cells that were used to store royal regalia, jewels, documents and other artefacts of Vasili III and Ivan the Terrible. Next to it is the Church of the Intercession that dates back to the middle of the 16th century. It served as a private chapel of tsar Ivan the Terrible. Famous Russian ruler ordered painting of frescoes on the walls of the church. They depict Russian princes and martyrs along with Old Testament kings and saints.