A visit to Alcântara makes a great day trip. An hour's ferry ride north across Baía São Marcos, the village of Alcântara is a curious thing, a struggling small town living inside the ruins of a once-thriving colonial city. In the boom years of the 18th and 19th centuries, Alcântara was a regional capital, the place where the merchant and plantation elite kept their families and traded their sugar and cotton. With the end of slavery in 1888 the plantation economy crashed and the merchants and planters fled, leaving the half-empty city in the hands of newly freed slaves and their descendants.
In 1948, the half-empty city was declared a historic site, primarily for its lovely collection of colonial houses with ornately decorated doors and coverings of bright Portuguese tile. Called "Windows and Doors" (in Portuguese Portas e Janelas), the style is both functional (the tile reflects the heat) and extraordinarily pretty.
A visit to Alcântara involves strolling down the main cobblestone street that leads from the port up the hillside through a series of small squares to a beautiful ruined church on a hilltop. Along the way there are hundreds of beautiful houses to admire, and at least six ruined churches to poke about.
There are also three fine, small museums. The best, the Casa Historica do IPHAN Seculo XVIII (the IPHAN 18th-Century Historical House) (Praça Gomes de Castro s/n; no phone; daily 9am-2pm) is a huge colonial mansion filled with paintings, porcelain, furniture, and all of the belongings of a rich merchant family, including the still-intact slave quarters in the interior courtyard. Guides do an excellent job telling the history of the house and the families that built it. Admission is R$1 (US50¢/£.25).
Everything in Alcântara is very laid-back. Local residents pretty much leave you to wander their city. There are a few gift shops and numerous small restaurants, which make good places to do as the locals seem to be doing -- trying to keep cool in blazing heat.
Brazil's satellite-launching center is just 5km (3 miles) away, but has been off-limits to visitors since a rocket blew up on the launchpad in 2003, killing 21 technicians. There's a visitor center in the town, but it's not worth visiting.