Israeli archeologists had a surprise when they were unearthing an 8th century CE mosque in Tiberias. They discovered the foundations of a 7th century CE mosque underneath it!  They also found coins and pottery which helped to date the older mosque – the world’s oldest to be excavated.

https://www.timesofisrael.com/one-of-the-oldest-mosques-in-the-world-uncovered-in-tiberias/