Which stringed instrument was once made so large tht it required two people to play it?

The instrument you’re referring to is the "octobass." This oversized string instrument, developed in the 19th century, is significantly larger than a double bass and requires two musicians to play it: one to handle the strings and the other to operate the fingerboard. The octobass produces deep, resonant tones and is primarily used in orchestral settings, making it a unique addition to the string family.