There's a clue in the title, the Sherborne Steam & Waterwheel Centre houses a horizontal steam engine and a waterwheel, and not a huge amount else.
The massive 26 foot (8 metre) diameter waterwheel was installed in 1869 to provide clean water for the inhabitants of Sherborne. It ran until 1959. It is unusual in that it was feed by three different leats, making the site quite difficult to understand.
In 1876 it was supplemented by a Hindley Steam Engine. Although that machine has not survived, the volunteers at the center have installed a similar engine which can be seen running, along with the waterwheel on selected open days.
For details of open days, times and admission prices, please see the centre's official site, detailed below.