I had never thought of going to another country, but we learned that it is easy to get there by just crossing the river, so we decided to try.
We had bought the tickets, including the walking tour, at the agency called Sea Cat in the centre of Buenos Aires.
It cost about 1,400 pesos (£42, €48, $56) per person.
The departure time was 12:30pm but because we were not familiar with the place, we went early to the Buquebus Terminal in Puerto Madero.
First, we had to queue to exchange our voucher with the tickets.
That was actually the check-in and some people with big luggage bags were handing their bags to the staff.
Then we went upstairs to have the security check and the passport check.
The officials from Argentina and from Uruguay were sitting next to each other and I got two stamps in my passport.
Now all we had to do was wait, so it was very easy.
After a while, people started queuing and we joined them.
The queue stretched all around the waiting room, but some people were still sitting.
When the queue started moving, those who were sitting and the ones towards the end of the queue dashed for the entrance to cut the queue, but one member of staff was there to stop them.
The boat was big, but after we sat down, I saw people walking around looking for seats.
There was a duty-free shop selling cosmetics and others things on the boat.
During our journey, the only things we could see through the dirty windows were the brown La Plata river and the blue sky.
The boat left 15 minutes late and it was about 13:45 when we arrived at Colonia del Sacramento in Uruguay, the town which is just across the river from Buenos Aires.
Because there were so many people, it took a long time to get off the boat, so it was after 2pm when we learned that the next English walking tour would start at 4pm.
“In that case, we have to have lunch” said my husband, who treasures food, and he started looking for a restaurant, checking the websites.
He started walking briskly straight towards the restaurant he had found on the internet, not looking around at the views.
Although Colonia is a small town, it took us a long time to find the restaurant and, in the end, we found that it was closed.
Because the time was limited, we felt pressed.
We decided to go to an alternative restaurant called A la Pipetua!.
It seemed that the paella was their speciality, but I had a chicken dish and my husband had stewed beef which was called Stroganoff, which we drank with Sangria.
The interior was nice and bright.
The waiter asked me “Are you from Sao Paulo?”.
It was out of blue and I just thought “Why??”, but afterwards I realised that he thought I am one of the Japanese immigrants in Brazil.
After satisfying our stomachs, we went to the meeting place on time for 4pm.
Colonia del Sacramento is a pretty, historic town, listed in the Unesco World Heritage sites.
There were a great many tourists from Buenos Aires, which is only one hour away and it was the weekend.
In the main square, some couples were dancing something like the tango.