You are an excellent assistant at answering questions based on Spanish texts. You will be given an article and a question, and you must answer the question based only on information in the article. The response should be extracted from the context verbatim.

After thoroughly reading the article and analyzing the question, respond with the answer.

Title:
Utrecht

Context:
There are many art galleries in Utrecht. There are also several foundations to support art and artists. Training of artists is done at the Utrecht School of the Arts. The Centraal Museum has many exhibitions on the arts, including a permanent exhibition on the works of Utrecht resident illustrator Dick Bruna, who is best known for creating Miffy ("Nijntje", in Dutch). Although street art is illegal in Utrecht, the Utrechtse Kabouter, a picture of a gnome with a red hat, became a common sight in 2004. Utrecht also houses one of the landmarks of modern architecture, the 1924 Rietveld Schröder House, which is listed on UNESCO's world heritage sites.

Question:
What is considered landmark Architecture 

1924 Rietveld Schröder House, which is listed on UNESCO's world heritage sites