User blog:RealgrandpaJoeWCG/Your Detailed Place VS. My Detailed Place. HELP

I'm making this a blog because i think it would get viewed more or quicker that way or at least I think so. Anyways i'm in need of some serious advice on building a place. Whenever i visit someone elses place, say like a popular hangout place or a city/town. It's got a lot of nice detail, really big space and a lot of area, etc etc. but whenever I myself try to pull off making such a place like that, it results in extreme lag. I don't understand how you builders avoid lag and still add all you want to your place(s). I know it's not my computer because like i said, i visit a nice detailed place and it runs fine. So can anyone please give me advice on what i should do? I have a house i've built and i rennovated it so it has less bricks. I found out my house has had over 10,000 bricks to complete the house, so i fixed it and got down to around 4 or 5 thousand bricks. But it still lagged for some reason after complete rennovation.