Stuck in Europe? Do some sightseeing with the help of a free city guide app

To help out stranded travelers, Lonely Planet announced a Volcano Relief Sale: 13 City Guide apps, which normally cost up to $16 apiece, can be downloaded for free to your iPhone.

Per Lonely Planet's announcement, the guides can be downloaded at iTunes by anyone free of charge through Thursday, April 22. The 13 European city guides are:

Amsterdam

Barcelona

Berlin

Budapest

Copenhagen

Istanbul

London

Moscow

Munich

Paris

Rome

Stockholm

Vienna