Petropolis is known as the Imperial city, as this was where the Emperor, his family, and their court used to escape the summer heat in the 1800's. The town still has a European feel to it left over from these days.
The journey begins by driving through the outskirts of Rio. After this, the road twists and winds its way up through the lush and tropical forest known as "Serra de Orgoas". The scenery is dramatic, with one side of the highway dropping away steeply. Try to sit on the left hand side of the bus on the way up, as this will offer the best view. Don't panic about the driver overtaking on all the blind corners, as the road is actually a separate highway for each direction.
When you arrive, you will really enjoy the change of climate. It is really crisp and a real change to the humidity in Rio.
There are many museums and residences of the Royal family, including the Cathedral and the Imperial Museum. It gives you a glimpse of what life was like in the 1800's, life for the wealthy anyway.
If you visit the Tourist Information Centre in the centre of town, they are super helpful and speak many languages. They can furnish you with walking maps that guide you to the main tourist sites, 11 in total.
There is no need to take an organized tour. It is easy and much cheaper to go there yourself. Take the local bus to the main bus station for about 1 real each way. Buses leave with either Facil or Unica buslines about every 15 minutes. The cost is about 6-7 reals each way.
This trip does give you another view of Brazil aside that of the beach if you are spending all your time in Rio itself.