In the 10 years since the Sept. 11 terrorist attacks on New York and Washington, the national landscape has changed in so many ways. Politically. Culturally. Physically.

The National Sept. 11 Memorial in New York (yfrog photo via @whitneyshefte)

Have government buildings been closed off in your area? Is your commute different? Are there artistic displays or memorials in your neighborhood? Please use the hashtag #911changes to describe how the world looks differently to you because of 9/11.

We see the large changes with memorials rising to pay tribute to the victims — the Pentagon Memorial opened in 2008, the permanent memorial of Flight 93 was dedicated September, 10 in Somerset County, Penn., and a national memorial honoring the 2,982 killed in the New York attack opens to families September, 11. These are all concrete signs of our collective mourning, transforming sites of tragedy into places of remembrance.

But there are other signs of change in a post-9/11 world. The Pennsylvania Avenue barricades that became permanent after the attack. More barricades and security signage at airports. Impromptu memorials across the country, the world, and online. Follow along as we collect #911changes in the Twitter stream below and check out a slideshow with photos that people has sent in commemorating their memories.

YOUR TAKE: What’s changed?

Tweet How did 9/11 change your world? Give us your thoughts by using #911Changes on Twitter.

More on Sept. 11 anniversary »

Post series: Nine lives, ten years later

The Age of 9/11: Using your age to examine the story

Photos: A day that changed America

Religion: What we’ve learned

Events: A list of D.C.-area memorial ceremonies