It depends on what you like the most! :)
Here, you may find old churchs (such as the last Gothic Church built in the World - in São Paulo), ruins (Missões), fortresses (in Recife, there are many built in the 15th century), nature paradises such as beaches (Northeast states, Santa Catarina, Rio de Janeiro) and forests (Mato Grosso, Amazonas, Rondônia), cities in mountain ranges (Gramado, Canela...). Besides all that, there's also the history and culture inherent to each of our capitals (each state has a capital) - Porto Alegre, São Paulo, Rio de Janeiro, Recife, Salvador, Belo Horizonte.
Brazil is a country of many flavors :)