Once , long , long ago , almost forty years back , he passed through ravenna and sent me a postcard of one of these famous mosaics .
曾经在很久很久以前，大约四十年前吧，他经过拉文纳时给我寄来了一张这些著名的马赛克的明信片。
Ravenna is famous for its mosaics ; hordes of tourists move from one church to another , craning their necks to glimpse the dim lustre of tiny multicolored smalti high up under dusky vaults .
