I am looking for an app that is not necessarily to be an educational tool but something really helps users and makes learners joyful. I notice Google Art & Culture. It combines aesthetic appreciation with language learning.
It has different categories and the content in each category updates regularly. For example, under the theme of Mosaics, 12 masterpieces with mosaic patterns are displayed on the page with both pictures and text description. By reading the articles, learners can enjoy an online gallery and gain some knowledge of the art, and also, implicitly receive authentic language input.
This app is not just a silence exhibition but it links to different youtube videos, for example the interview to the musician or dramas which reappear a certain period of the time.