April 18 is International Day for Monuments and Sites (World Heritage Day).

The International Day for Monuments and Sites was proposed by the International Council on Monuments and Sites (ICOMOS) in 1982, and it was approved by the General Assembly of UNESCO in 1983. 

The aim is to promote awareness about the diversity of cultural heritage of humanity, their vulnerability and the efforts required for their protection and conservation, according to Calend.ru.