This is an entry for Turkey's Çanakkale Antenna contest and it looks pretty insane. The 328 foot high design would take passengers in a glass pod on a roller coaster loop. How will they even build this tower?

This 328-foot (100-meter) structure wasn't the winner of the Çanakkale Antenna contest, a communications tower that will be built in Çanakkale, Turkey, though, but what a sight it would be, and what an engineering feat.

According to its creators, the architecture studio AL_A:
A pioneering move to split the antenna in two became the creative technical solution to unlock the potential of giving visitors the unique opportunity to ascend to the very top of what would otherwise be an ordinary telecommunications tower and allowing them a three dimensional spatial experience within the imaginary threshold of East and West.

Visitors ascend almost 100m to the pinnacle of the Tower in gondolas fixed to a track within the structure, with interest at every height as visitors travel up to the highest point of the Tower before descending the opposite side.
ArchDaily has a selection of the other proposals. Check out another two below: