Useful information about Zagreb can be found on official site of The Zagreb Tourist Board.
"The treasures of history are kept and exhibited in the museums of Zagreb. Apart from objects related to the history of the city, the Zagreb museums and art collections possess exhibits from the whole world round of very considerable historical and artistic value. Things of particular rarity are the Zagreb Mummy with the world's longest text in Etruscan, and the remains of Neanderthal prehistoric man (homo Krapinensis)." (Source: Zagreb Tourist Board)
"When the city lights go on and the daily tempo lessens, you might find your way to one of Zagreb's theatres. Especially if you do not speak Croatian, this theatre might be the National Theatre where there are performances of opera or ballet for both of which it is famous. Each theatre has its own repertoire, and all together they show the richness of Zagreb theatre life." (Source: Zagreb Tourist Board)