Prerequisites: Stable Level 20, Rally Point Level 10, for Romans only

The horse drinking trough of the Romans decreases the training time of cavalry and the upkeep of these troops as well. It can also be built in Roman Wonder of the World villages.

The Horse Drinking Trough in detail:

• Accelerates the production time of cavalry units by 1% per level
• Lowers the crop consumption of all Roman cavalry units in that village
• Equites Legati consume one crop less at level 10
• Equites Imperatoris consume one crop less at level 15
• Equites Caesaris consume one crop less at level 20

The level dependent attributes (such as construction costs and generated culture points) can be found here.
For the full table of construction times click this link for server with 1x speed, this link for server with 2x speed and this link for server with 3x speed.