Just some quick add-ons as Cologne zoo is one of my favorites...
The uakari wasn't a red but a white-headed uakari (Cacajao calvus)... They had a pair coming from Stuttgart zoo. The male, Pucky (who lost and eye and really looked weird) died in july 2005 and the female, Schneckchen, died a few months after. They were kept in the small south-american monkey house (which looks like Moscow's cathedral)... in here, you can find one of the biggest breeding groups of red howler monkeys (Alouatta seniculus), yellow-breasted capuchins (Cebus xanthosternos) and Geoffroy's spider monkeys from a very rare subspecie (Ateles geoffroyi ornatus).
You can also look for the meerkat enclosure (I know it's definitely not a rare specie!!), it's one of the best and biggest around Europe.
They also have an impressive duck collection (with Madagascar endemics Anas bernieri and Anas melleri breeding).
The last douc langurs in Europe (with a baby born earlier this year) and the very last saiga antelope (a male) are also on exhibit.
In the Madagascar house, you'll see some rare species, Greater bamboo lemur, White-bellied ruffled lemur, Crowned lemur...
The pheasantry holds some very rare species including goliath herons, cape bald ibis, white cranes and some madagascar endemics (crested ibis, blue coua, crested coua, madagascar fody) transferred last year from Walsrode.
Close to the big-cats enclosures, you'll find some rare siberian weasels (Mustela sibirica).
The big tropical house is trully impressive... nice collection (Lesser whistling duck, javan pond heron, Rodriguez fruit bat, Vietnam pheasant, Palm cockatoos ....).
And to finish... don't forget to visit the aquarium-reptilarium-insectarium... incredible collection and some trully rare species there!!!
Have a nice visit!