The objective of the TOWR (pronounced “tower”) is the development of a time distribution service via optical fibre over the Madrid region, based on time generation from very stable clocks (hydrogen masers), GNSS time-transfer (including GPS and Galileo) to UTC(k) laboratories, and White-Rabbit technology (an extension to the IEEE-1588 PTP protocol). The activity aims at demonstrating a robust and accurate “Time-as-a-Service” (TaaS) concept. An increasing number of applications require accurate, reliable, and traceable signals for time and synchronization, normally aligned to Coordinated Universal Time (UTC). Key fields of application are banking and finance, mobile telecommunication networks, and energy grids. The TOWR is proposed as a pilot project for a first customer in the financial market: the Madrid Stock Exchange (Bolsa de Madrid) covering a distance of around 50 km.