The stones of Jerusalem’s Western Wall are receiving injections, with medical-like syringes. Each 2000-year-old stone is inspected six-monthly for signs of weathering. Those needing repair are delicately injected with a liquid, limestone-based grout to protect the wall for at least another 2000 years.
https://www.jns.org/western-wall-stones-get-injection-before-passover/