One of the grandest monuments in DC which dominates the skyline is the National Cathedral, also known as the Cathedral Church of St Peter and St Paul (Episcopalian). As the 2nd largest church in the United States and 6th in the world, that comes as no surprise. It also holds the record as the highest point in DC, a fact that's easy to believe when you stand on the 7th floor observation deck surveying the entire city!
The idea was rooted in Pierre L'Enfant's 1791 plan of DC for the need of a church of national significance. It wasn't until 1907 that construction began (with President Theodore Roosevelt presiding the foundation laying ceremony) and the Cathedral was officially 'finished' in 1990 with President George H W Bush in attendance. It has indeed been of national importance as it has been host to numerous state funerals and memorial services.
The original architect was Frederick Bodley, a well-known English architect, who was replaced upon his death after WWI with Philip Hubert Frohman - who developed and expanded upon the original plans. Much like it's predecessors, the great European middle age cathedrals, the style is primarily gothic. However, the difference lies in the fact that while the churches in Europe were built over centuries (explaining their varied styles throughout the buildings), the national cathedral was purposefully built as a 'hodgepodge' to appear like the precedents: So a 'fake' evolved style if you will. It makes it all the more interesting!
What I love most about the building though is that while it is rooted in the gothic cathedral tradition, there is a lot of our modern world at play. Many of the stained glass windows and sculptures depict our modern age: robots, space travel and even Darth Vader!
The National Cathedral is, to me, an Opera of a building. By that I mean it combines all the arts into one package: secular and religious, modern and antique, embroidery, stained glass, architecture, sculpture, gardens, painting. You name it, they have it. Not to mention the views of the city!
Now for some of the delicious details. The one side transept (I forget which and both are different) has this beautiful blue ceiling. I love the juxtoposition of patterns! In the pictures above, you almost sense the scale of the space, ENORMOUS. I love the groin vaulting in the ceiling and the way the stained glass adds so much color to the Indiana Limestone interior.
Like all good gothic cathedrals, here are the flying buttresses behind the rear chapel.
I loved the adjoining buildings of the cathedral school - like an old English country manor!
The basement level is of course a bit gloomy, but full of as many details and workmanship as the rest of the cathedral. I loved this view looking up the stairs into the main church.
In this capital on the outside, you see a bit of the modern 'edge' - a robot amongst the figures!
As our national cathedral, much of our countries history is depicted. This statue of Abraham Lincoln rests in the front of the nave.
Above one of the interior front doors is Eleanor Roosevelt among some others who are celebrated for their good work.
I loved this modern iron gate down in the basement. The handle is a large iron hummingbird.
The craftsmanship of everything in the building is breathtaking. Even this simple handrail is so elegant. 
Thousands of hand embroidered cushions fill the space -each one amazing in its' own right. This one fits with the space travel themed stained glass windows.