hotbed
n
1 bed of earth heated by rotting manure to help plants to grow （用粪肥发酵产生热量的）温床.
2 (fig 比喻) ~ of sth place where sth evil or undesirable is able to develop easily and freely （有利於坏事物滋生发展的）温床
a hotbed of vice, crime, intrigue, etc 罪恶、 犯罪、 阴谋活动等的温床.