Once again, there are a whole bunch of great entries. I'll just add some of mine. "Doors with History".
This the the gatehouse to Richmond Palace at Richmond-on-Thames, outside London. It was the site of a Royal residence from 1125 AD. King Henry VII built a magnificent Tudor Palace and this gatehouse around 1525. His coat of arms is above the large arch which was used for carriages and carts as well as men on horseback. The smaller gate, now bricked up, was for people on foot. The large arch was closed with two huge wooden doors, but during the civil war of 1642-1651, Oliver Cromwell's army smashed the gates and burned the palace. The area is now used for private homes.
The magnificent entrance to the Victoria & Albert Museum in London. This entrance was built in 1899 and Queen Victoria laid the foundation stone.
The South door to the Templar Church in London, made famous by Dan Brown in
The Da Vinci Code. The round church, which is now the nave, was constructed in the late 1100's and consecrated in 1185 AD by Heraclius, the Patriarch of Jerusalem. King Henry II attended the consecration. The rectangular Chancel was added around 1235 AD. Until 1307 when the Knights Templar were dissolved, candidates for the order would enter this south door at dawn and move to the round nave for their secret initiation ceremonies. The Temple Church is still a functioning church and is also popular for organ recitals and choral music.