Hello,

this is NASA's crawler transporter used for carrying spacecraft from the Vehicle Assembly Building (VAB) to the launch pad.
Rockets and space shuttles get assebled on the Mobile Launch Platform (MLP), which then is carryied by the crawler transporter.
The crawler transporter weighs 2721 tonnes and is able to lift three times its own mass which equals 8164 tonnes.
It is propelled by 8 tracks being connected by hydraulic cylinders to the vehicle chassis. This allows for independant height adjustment of each corner of the vehicle. Height adjustment is needed when the transporter crawls up the ramp to the launch pad and the rocket is meant to stand upright.
There are two control cabins, one for each direction of movement.
When loaded, the maximum speed is at 1.6 km/h (1 mph) when unloaded 3.2 km/h (2 mph). So, you can easily keep up to it simply by walking.
In total there are 2 such crawlers in the world and they are after bucket wheel excavators the second largest vehicles ever built.
They were manufactured by the Marion Power Shovel Company which used to make steampowered excavators like the Marion Steam Shovel.

Enjoy!