Porto

Luis Bridge

After that you could board the Funicular dos Guindais to get down to the waterside

Porto Cathedral

São Bento train station - like an open museum

Church of Santa Clara

Market place

Majestic Café

Clerigos Tower

University of Porto

Livraria Lello (suggest buying a priority ticket)

Jardim do Palácio do Cristal

Cais da Ribeira

Igreja do Carmo

https://www.thecrazytourist.com/25-best-things-porto-portugal/