Alex has given some very good suggestions. Let me add my two cents.

Iguazú itself is not dangerous. What should be avoided at night and be very careful during the day is the Paraguayan town of Ciudad del Este and the bridge to get to it. There is a lot of thievery and the like.

First and foremost - Iguazú Falls are never dry. I was there in June a couple of years ago - when it does not rain. They were fantastic! Heavy rains occur in September and October - then there is even more water. They are much larger and have a greater volume of water than Niagara Falls.

Both countries - Brazil and Argentina - hace national parks bordering the river and the falls. Both sides are worth seeing but the view of the falls is more dramatic from the Argentinian side. They have wooden walkways that take you very close to the falls and a fabulous panorama.

When the Itaipú Hidroelectric Plant was built - it is still the world´s largest - it canceled out part of the falls - what was called Sete Quedas - 7 Falls. Loads of people went there to literally say good-bye to them. They were beautiful. The Hidroelectric provides electricity for Brazil, Argentina and Paraguay. It can be visited.

We stayed at the Sheraton on the Argentinian side. It is within the park with marvelous views of the falls and awalking distance to them.

Pantanal is totally different - it is flat as flat can be!! Best time to go there is from May to September - dry season - best for wildlife. March to October is the best time for fishing - when and where it is allowed. October to February is the rainy season. March and April the waters recede and wildlife "appears".

Actually the National Park of the Pantanal is two parks - the Pantanal North and the Pantanal South. The road that connects them runs on the outside of the park along the eastern border.

It is a much guarded area as far as humans are concerned - for the protection of the area and its wildlife. There are infinite species of land, water and air creatures. Boat rides are a must to really enjoy it. But do be careful - my son-in-law almost fell off a pier in a place that was simply full of "jacarés" (~crocodiles) - and it was my daughter that almost died of fright!!!!.

One thing is a MUST - yellow fever vaccine at least 10 days prior to traveling. That goes for everyone, Brazilians included.

There is a town - Bonito - about 120km from the southern boder of Pantanal South which is famous for its natural beauty: parks, waterfalls, lagoons, grottoes, etc.

You will enjoy this trip - they are great areas. Come October I will be in Boston, enjoying the MA fall foliage.

Regards, Susana São Paulo, Brazil