The Gladiators From Capua by Caroline Lawrence 

The story is set 2000 years ago in ancient Italy, just after the great fire that destroyed part of Rome. Flavia, Nubia and the puppy, Tigris, mourn for the supposed death of their friend Jonathon. Then an invitation arrives asking them and the dumb ex-beggar boy, Lupus (who has heard of a boy matching their missing friend’s description), to attend the Hundred Day Games in the great Coliseum. Here the friends meet exotic animals and fierce gladiators but will they find Jonathon? Read the book to find out! This book is the sequel to The Enemies of Jupiter and would be of interest to children in the eight to twelve age range. As well as being a cracking adventure story, it also contains a wealth of information on ancient Rome and a comprehensive glossary of Roman terms.