Belém, Portugal, is located on the Tagus River, which empties into the Atlantic Ocean. I took a daytrip here during my stay in Lisbon on the 2020 solo European trip. This was part of my stayover provided by TAP AirPortugal.
I visited Jerónimos Monastery, the Jardim da Praça do Império, the Rose Compass, the Padrão dos Descobrimentos, then walked along the promenade. I stopped at a cute little food truck called Mister Tapas to relax, have a sandwich and some wine.