The Ammonite Watchtower is a small but old archaeological site in Amman, built as a circular defensive tower by the Ammonite kingdom sometime between about 1000 and 500 BC. It is not a large ruin, but it gives a tangible link to the city's pre-Roman layers.
It works best as a short stop for visitors who enjoy ancient sites beyond the Citadel and Roman Theatre. The remains are modest, so treat it as a quick detour rather than the focus of a day.