Inside Brick Building No. 5 (赤れんが５号棟), the park's largest building. Built in 1918 to store torpedoes, depth charges, and mines. After the war, it was used by a warehouse company.

Now used as an event hall and cafe space (cafe open only on weekends). It can be rented to hold exhibitions or events (concerts, weddings, etc.). It has been reinforced with these steel girders for earthquake resistance. National Important Cultural Property.