Wellington Blockhouse

I drove past this building on the way to Tulbagh this morning. Any ideas what it was /is used for? I passed another further along which was also in a vineyard. The R44 was pure delight with so many spring flowers on display, and miles of lilies.
When I got to Tulbagh I got lost! This must be a record as there is only one main street. I back tracked and did a u-turn when I spotted a tourist information board. I was so busy looking ahead that I did not notice that there was a canal and not a pavement on the side of the road and ended up with my front wheel in a ditch. Groan. I wasn't sure what to do, but within minutes 6 strong rural men appeared, gave me some instructions and quickly lifted my car out the ditch. Fortunately no harm done to the car. What a blessing,