The house was built just before the Mexican Revolution, and had a turret added during revolutionary times so that a watchman could alert the owners if soldiers of whatever faction were in the area. Most Mexican houses have a large wall around them, so it was probably the watchtower that made Trotsky decide to take over the property in 1939. 

The house's defenders repelled one major attack in May 1940, and the bullet holes can still be seen in the inside of the house, including one right over Trotsky's bed.

Following his assasination in August 1940, his body was cremated and the ashes placed in a grave that can be found in the garden. 

If you are intererested in twentieth century political history, the house deserves a visit. It is located at Viena 45, but the entrance today is around the corner at Churubusco 210. Take Metro Line Three to Coyoacan, and then wak to Churubusco, which is a main avenue.