This is the Hungarian sense of humor. Look carefully at the building behind the Shell sign. It is actually an optical illusion created by painting a wall, but from this angle it is almost perfect. Note on the left in the third picture that there is a real person on a third floor balcony looking around the side of the building from the back.
From the angle of the left picture the illusion is beginning to suffer. The right picture is the same building, looking about half as long -- but that's how long it really is.
We have no idea what this was. They were quite scruffy. Probably commemorating something historical, at a guess.
The first picture shows how the ancient ruins of a Roman building were built into the fabric of a new building.
