A must see if you come to Rio. Plan to spend 3 hours or more here. Cacti section, tall palms, lake with massive fish...But its really well done. Also enjoy the views up to Christ the redeemer.
You can get a bus direct from Copacabana and Ipanema.
Up the road 15 minutes is Parque Lage, interesting for its main building inside and there is a treck which goes all the way up to Corcovado ! Not often made these days but the path is good. It takes a good pair of hiking boots but I did it in flip flops in 1 hr 30. You should take hiking boots and take longer to do it.