Lisbon is all about the river. The Tejo is present in history, in the economy, in daily life, and it marvels tourists every single day with its shining, ever changing shades of blue, green and gold. It is also the daily commute of thousands of people who live on the other bank and cross the river everyday to go to work in the big city.
Want to feel like a local? Jump on a ferry, using your Lisbon Card, and go check if the water is bluer on the other side. There are different stations and crossings, with slower or higher speed ferries, have a look at the schedules and try to go off the peak times to enjoy the views unbothered (https://ttsl.pt/passageiros/horarios-de-ligacoes-fluviais). Get your camera ready, the angles and perspectives are endless.
On the other side, you can just stroll along the water, take a bus to the giant statue of Jesus Christ blessing the city of Lisbon and go up to the top to enjoy the breathtaking view you probably also saw from the plane when arriving. Or you can head to a truly different restaurant called “Atira-te ao Rio” (http://www.atirateaorio.pt/), a 10-minute walk from the ferry. The name means “throw yourself into the river”, but it is of course just a metaphor for its proximity to it. You will dine with your feet literally in the water.