Historic sites Conservation and restoration 45 Historic buildings 44 History 15 Congresses 11 Architecture 9 Historic preservation 9 Law and legislation 8 Bibliography 7 Antiquities 6 City planning 6 Monuments 6 Cultural property, Protection of 5 Cultural property 4 Description and travel 4 Heritage tourism 4 History, Local 4 Landscape protection 4 Protection 4 Tourism 4 Buildings, structures, etc 3 Conservation of natural resources 3 Environmental protection 3 Guidebooks 3 Natural monuments 3 Pictorial works 3 Collection and preservation 2 Interpretive programs 2 Natural areas 2 Nature conservation 2