Unce upon time ... I visited Spišský hrad (medieval castle in north Slovakia). I wondered how heavy, strong and robust were windows and gates of this fortres. To understand I made simple model from wood.
You can play with it and find out why are old bridges so heavy, or how important is to have reliable base.

Steps:

Take wooden stick 5x3 cm and cut 2 litle and 5 larger parts. Take dimensions from this chart:


Put smal parts on floor and add first "brick" ...


... then second, third, fourth ...


... and finish.

Voila!


If you like it, you can prepare another models: