Alex Kapranos (Franz Ferdinand) wrote about Zagreb on his blog: http://bit.ly/nO3yin
Source: www.guardian.co.uk
Located at the top of Opatička Street, Popov toranj (Priest's Tower) is an old fort located in Zagreb's Upper Town. It was built in the mid-13th century after Tatars' invasion for fears that such an invasion might happen again. The people called it the Priest's Tower because it belonged to the Bishop of Zagreb. In the first half of the 16th century the tower became part of the city fortification, and it had the task of protecting the northern city gate. In the mid-17th century it housed a school, while the second floor was added in the first half of the 19th century. Today, Popov toranj is the place where you can almost "reach" the stars. At its top there is a dome, which has been the home of Zagreb Observatory for more than a hundred years, ever since it opened on December 5th 1903. The city fathers rightfully decided that Popov toranj was the ideal location for the observatory because it sufficiently rises over the city to enable its telescope to be above the lowest, more polluted parts of the atmosphere, providing a clear view of the sky, while still being located virtually in the centre of Zagreb. A pleasant walk from one of the city's main streets is all it takes you to get there.
Visiting hours: Tuesdays-Fridays from 8 until 10 p.m.