Many private travel agencies organise walking tours with English-speaking guides, as well as excursions out of town, including Zig Zag Holidays (tel: (02) 980 5102; website: www.zigzagbg.com), Tourist Service Holding (tel: (02) 816 9580; website: www.tourist-service.com) and Balkantourist (tel: (02) 987 5192; website: www.balkantourist.bg). The tourist office (tel: (02) 933 5845/11; website: www.bulgariatravel.org) can also help arrange tours. An organised walking tour of the city centre, however, is largely unnecessary, as the historic sights are all concentrated around ploshtad Sveta Nedelya and are well marked, making a self-guided tour the easiest and cheapest option.