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:
Newcastle_upon_Tyne

Context:
Throughout the Middle Ages, Newcastle was England's northern fortress. Incorporated first by Henry II, the city had a new charter granted by Elizabeth in 1589. A 25-foot (7.6 m) high stone wall was built around the town in the 13th century, to defend it from invaders during the Border war against Scotland. The Scots king William the Lion was imprisoned in Newcastle in 1174, and Edward I brought the Stone of Scone and William Wallace south through the town. Newcastle was successfully defended against the Scots three times during the 14th century, and was created a county corporate with its own sheriff by Henry IV in 1400.

Question:
How high was the stone wall built around Newcastle in the 13th century?

25-foot