Describe the land of Houyhnhnms.

Houyhnhnm is where Gulliver fell in love with a people and its culture. This island is run by advanced horses that teach Gulliver how evil humanity is and also how flawed. Gulliver spends Part 4 in this setting and in the timeline of the book he spends 5 years living with them. He never plans to leave but they send him away.

From the text:

The land was divided by long rows of trees, not regularly planted, but naturally growing; there was great plenty of grass, and several fields of oats.