After returning to Brazil from Colombia, we made a quick stop in Rio de Janeiro, just for one night. We had to repack our backpacks and grab some new clothes. It was also the perfect time to wash other things. We then moved on to São Paulo for 2 and a half days, from where we continued our journey to Argentina. Here the second part of our LATAM journey began. We arrived in Buenos Aires at 10 p.m. and at the airport we were greeted with a surprise at border control. Namely, we received the wrong departure stamp from Bolivia, so the local border guards questioned and checked one of us for a long time. Fortunately everything was fine with the other one of us and we both had all the required documents, so they let us in. Another thing that greeted us in Argentina was the high prices. There are two airports in Buenos Aires, Ezeiza International Airport, the one we chose, which is the main international airport and is about 50 kilometres from the city centre and Jorge Newbery Airfield, which is popular for domestic flights and some international flights to and from nearby countries, which is located in the city by the river. So our first Uber ride in Argentina cost us more than average, as did our first dinner after checking into the hotel. 
Interestingly, Buenos Aires is not on the ocean, but along the banks of the Rio de la Plata, which is considered by some to be the widest river in the world. On the other hand, it is an estuary, so a partially enclosed coastal body of brackish water into which two rivers, the Uruguayan and the Parana, flow. Naturally, it has a free connection with the Atlantic Ocean. On our first day we visited the Recoleta district, which is famous for its Parisian-style townhouses, and its main tourist attraction is the Recoleta Cemetery, which contains the tombs and mausoleums of prominent people such as Argentine presidents, politicians and Nobel Prize winners. In the afternoon we went to the Puerto Madero district, which is a central business district full of tall skyscrapers and converted red brick buildings serving as exclusive steakhouses. Such an exclusive district only for the rich. The next day, we saw the La Boca neighbourhood, which is home to the Boca Juniors football team, so it's full of graffiti and football bars. It's the complete opposite of what we saw the day before, as it's a district for rather poorer people, so the vibe is completely different. We also had the pleasure of meeting a Polish semipro runner- Wojciech Kopeć, whom we spotted by chance on the street. He had just finished his training camp in the Argentinian mountains and came to Buenos Aires to take a plane back to Poland. It was a very nice meeting, because apart from running he is also interested in travelling, so we exchanged opinions about the countries we visited in South America. 
Before coming to Argentina, be aware of the divergent exchange rates in Argentina. Due to the monetary crisis of 2018, there is a huge black market where the exchange rate of the Argentine peso is about 100% higher than the official one. Basically, this means that it is better to bring dollars and exchange them in the black markets that operate on the streets, rather than pay by card, as banks use the official rate and you will pay almost twice as much.