The HYDRA Research Base is a research compound operated by HYDRA led by Wolfgang von Strucker and Doctor List in a fictional European country of Sokovia, housing numerous coveted items of varied origins and importance. It contains a occupied by Scarlet Witch and Quicksilver. It was also heavily defended, being equipped with an energy shield powered by Loki's Chitauri Scepter along with turrets augmented to fire Chitauri energy blasts. It was guarded by dozens of HYDRA troops equipped with Chitauri cannons, machine guns, tanks, trucks, and jetpacks. The forest around the base was also fortified with watchtowers and bunkers. Shortly after becoming sentient, Ultron traveled to the base to start replicating Chitauri technology and build his own army of Ultron Sentries.