I visited this site on my first day in Brazil, as it is easy to reach, being in central Rio de Janeiro. I was not expecting much of it, and to be fair, it was a little underwhelming. As land has been reclaimed in the harbor, the Valongo wharf lies about 350 meters inland, and it is very difficult to imagine how it used to be.
I usually don’t read too much about sites I plan to visit, trying to keep the excitement of the discovery intact. But for this site, it would have been better to research beforhand to better understand and enjoy the visit.
It consists of part of the old stone wharf in the former harbour area of Rio de Janeiro, built for the landing of enslaved Africans reaching the South American continent from 1811 onwards. An estimated 900,000 Africans arrived in South America via Valongo. In fact, they were first landed in central Rio de Janeiro for Customs, and the moved on Bom Jesus Island for quarantaine. Only after quarantaine were they taken to Valongo to be sold in slaves markets.

The site is composed of an archeological window, through which two main archaeological layers can be seem. The lowest level consists of floor pavings in pé de moleque style (irregular cut stone set directly on the sand), attributed to the original Valongo Wharf. Built in 1811, it was more a paved beach and remained in use until 1831.
In 1843, the original wharf was earthed over to build a new wharf in honor of the arrival of Princess Tereza de Bourbon, wife of the Emperor Dom Pedro II. Nowadays, the Empress Wharf makes the upper layer of the site with a little jetty, made of regular cobblestones pavement. An obelisk was also built for the Empress arrival, still standing (even though not in its original position).
In the early 20th century, the area was covered over to reclaim some 350 meter of sea. It was not until 2011 that archeological excavation was carried out to rediscover Valongo and Empress Wharfs. 

Although underwhleming at first, Valongo Wharf is an important physical trace of the arrival of African slaves on the American continent, and is an emotional tribute to thier suffering.