题目内容：

假定英语课上老师要求同桌之间交换修改作文，请你修改你同桌写的以下作文。文中共有10处语言错误，每句中最多有两处。每处错误仅涉及一个单词的增加、删除或修改。

注意：1. 每处错误及其修改均仅限一词:

2. 只允许修改10处，多者(从第11处起)不计分。

Welcome to the Great Wall. Measured more than 6,000 kilometers in length, the Great Wall is known as the long wall in the world. It had a long history of more than 2,000 years. That is amazing about the Great Wall is that it is main made of stones and bricks, and that all the construction was done by hand. As it was used to protecting the country from foreign invaders, every a few hundred meters along the Great Wall, there was a watchtower. Now, as a symbol of China, the Great Wall has become one of the most famous tourist attraction in the world. There is no wonder that the Great Wall attracts thousands foreign tourists every year.