Quiz a local on what the most unique structures in town are and they'll probably mention Santiago Concrete Water Tank. It's one of the first things you'll spot when you start exploring.
You'll have no end of sightseeing choices when in Santiago City. Santiago Concrete Water Tank is a great place to begin here, but there are lots of other interesting attractions to appreciate. Robinsons Place Santiago, and Santiago Memorial Park are close to the modern piece of architecture and will round out your day nicely.