In several places of Bukhara you can see the ancient city walls, which defended Bukhara from the enemy troops. It will be most easily to see the city walls at the Samanids Park, though there are other interesting sections of the surviving city walls with Talipach Gate.
In the Middle Ages Bukhara was enclosed by a ring of walls with 11 gates. Until 12th century the city walls were made of clay, and then of burnt bricks, which significantly increased their durability. Wooden beams were included in the center of the wall for strength.
Considering a great number of wars and invasions in the course of several centuries, the main fortifications, where the walls of Bukhara and the Ark Citadel belong, were often destroyed.
Until nowadays there remained only several sections of the wall dating back to 16 century, as well as 2 gates: Talipach and Karakul. The reconstructed section of the Bukhara city wall is at the Samanids Park. You can reach it on foot having went out on the shore of a large lake after visiting the Samanids Mausoleum.