The Alamo is special because of the battle that happened there, whiched played a part in the Texan war for independence. It is where a small group of soldiers tried to defend against Mexican soldiers with nine times their numbers. While they failed, they were able to hold the fort for about two weeks.
The Alamo is open for visitors from 9:00 AM to 7:00 Pm during the peak season and from 9:00 AM to 5:30 PM during the off season. It is free for all visitors.
To learn more about The Alamo, go to the link.