Outside the tower
The tower looks like an upside-down obelisk, supported by a base of smaller towers. On top is a roof formation that is suspiciously similar to a certain refuge in the clouds.
Inside the tower
Benham Tower is the reason the Guren Nash and his father moved to Benham City. His dad was recently assigned their to work on redesigning the Tower. Guren has been in the building at least three times, but claims he does not understand why his dad has to spend so much time on the tower. His dad is often busy working on the tower, and does not get enough time to spend with his son, as shown in "No 'I' in Team", when Guren's dad blew him off after promising to take him to the water park.
Black Dragon Key
The Black Dragon Key was also located at the tower, however, its presence was not detected by Gen or the workers because it was locked in a tenkai seal. After Beni lead the Knights to the Tower, Guren used his Bravenwolf Core Brick to eventually find it a the top of the Tower. They were then double crossed by Beni, who, along with Gen, stole the Key and took it to Quarton, where eventually Vilius used it to awaken the Black Dragon.
In the episode "Toxsa Blocked" it was revealed that Benham Tower was an anti-brickification device and Granox and Slyger were sent to destroy it. In the following episode the Tenkai Knights had to use their core bricks by inserting them simultaneously in order to reboot the anti-brickification system and the portal.