四害
'the four pests', i.e. rats, flies, mosquitoes, and sparrows; see also 打麻雀運動|打麻雀运动[Da3 Ma2 que4 Yun4 dong4]
四海之内皆兄弟
all men are brothers
四海升平
lit. all four oceans are peaceful; worldwide peace (idiom)
四海为家
to regard the four corners of the world all as home (idiom); to feel at home anywhere; to roam about unconstrained; to consider the entire country, or world, to be one's own
四海皆准
appropriate to any place and any time (idiom); universally applicable; a panacea
四海飘零
drifting aimlessly all over the place (idiom)
吕塞尔斯海姆
Rüsselsheim, city in Germany
放之四海而皆准
appropriate to any place and any time (idiom); universally applicable; a panacea
放之四海而皆准
applicable anywhere (idiom)
波斯普鲁斯海峡
the Bosphorus (strait)