My Mom has planted a beautiful, small garden over his grave:

My dad was the person responsible for taking huququllah payments and sending them to the holy land. Also for teaching about huquq to the baha'is in the country.
My mom hosted the Huququllah representatives from Central America (Costa Rica, Mexico, Honduras and El Salvador) for several days. They were in Costa Rica for a meeting and a conference.
Here's a picture of them visiting my dad's grave.