highest concentration of Art Nouveau architecture in the world
... that Riga contains the highest concentration of Art Nouveau architecture in the world ?
... that <a href="./Riga" id="mwAu4" rel="mw:WikiLink" title="Riga">Riga</a> contains the <b id="mwAu8"><a href="./Art_Nouveau_architecture_in_Riga" id="mwAvA" rel="mw:WikiLink" title="Art Nouveau architecture in Riga">highest concentration of Art Nouveau architecture in the world</a></b> <i id="mwAvE">(building detail pictured)</i>?