壮观： 1.an impressive grand sight; a glorious (or grand) view; a superb (or splendid) view 2.spectacular; superb; imposing 雄伟: 1.an impressive grand sight; a glorious (or grand) view; a superb (or splendid) view 2.spectacular; superb; imposing 壮观 and 雄伟 have very close meanings. So most time we could replace one by the other. And also they could be put together to show much deeper . But there are still some little differece here: We prefer to use壮观 to describe about scenery and to use 雄伟 to describe imposing manner. And of course, you still could replace each other. And nowadays, we seldom use 雄伟 to describe people, cause it's more anciente chinese way.

"壮观"修饰景象 as in "scenically spectacular" "雄伟"比拟形态 as in "structurally stately"

他们都解释很好了，不过我可以给个建议，如果你突然问我这两个词有什么区别，我也是说不出来的，但是我会去查字典，你有中文字典吗，没有的话，可以买一本中文字典，要全中文的。

壮观 雄伟的事物或风景[grand sight;magnificent sight] 雄伟 1.高大雄壮 “好一个英俊雄伟的干部，怪不得 兰英 一看见以后，回来是那么高兴！” robust 2.宏大壮阔 “但是，我却看到了一次最雄伟、最瑰丽的日出景象。”grand; imposing; magnificent; 3.杰出，不平凡 “...雄伟奇杰之才..." outstanding http://www.chazidian.com/r_ci_5d122781c36485d586c10880349105eb/ FYI

壮观 is a word describing scenery 雄伟 often uses for man`s character and some great scenes like mountains