The world's largest veterinary clinic is Salam Veterinary Group in Buraydah, Saudi Arabia. The facility covers 71,500 square meters (769,620 square feet), employees around 300 veterinarians, and can house up to 8,000 animals at once. The complex contains an equine hospital, a camel hospital, pet clinics, a wildlife center, and a research center. They also have branch offices and mobile units used for farm visits. The clinic was already huge when it was established in 2020 before it expanded in 2022 in order to achieve the Guinness World Record.
This clinic offers services you won't find elsewhere, like embryo transfer for specialized camel breeding, infertility treatment, paternity testing, and drug screening for banned substances. I can't find out much about their wildlife services, but you have to wonder if they provide veterinary care for Saudis who keep tigers and other exotic animals. You might notice that the header at their website in English reads backwards. That's because Arabic is read from left to right. Still, any way you look at it, this is a big hospital.
(Unrelated image credit: Prof. Mortel)