image credits

intro:
https://pixabay.com/static/uploads/photo/2015/03/14/14/27/video-673236_960_720.jpg


4)
https://www.flickr.com/photos/photommo/15171469614
https://www.flickr.com/photos/photommo/15752392516
http://www.philadelphiastatehospital.com/sitebuildercontent/sitebuilderpictures/picture12.jpg
http://www.panicd.com/encimages/839-8343792_f520.jpg
https://www.flickr.com/photos/sahrah/4073489677


3)
https://upload.wikimedia.org/wikipedia/commons/9/98/Bj%C3%B6rk_performing_at_Cirque_en_Chantier_1_edit.jpg
http://static1.squarespace.com/static/5461b00ce4b093c10ce76423/t/54cef4c9e4b0416d14add9bd/1422849231226/


2)
https://upload.wikimedia.org/wikipedia/commons/5/53/Catacombs_rueDeLaVoieVerte.jpg
https://upload.wikimedia.org/wikipedia/commons/2/2f/Catacombes_de_Paris.JPG
https://upload.wikimedia.org/wikipedia/commons/2/2c/Catacombs_of_Paris,_16_August_2013_015.jpg

1)
http://www.dahabdiverslodge.com/files/3313/8909/8941/Blue-Hole---El-Bells.jpg