Things change with the passage of time. There have been great many changes in the world. Seasons of the year keep on changing. They follow one another in a cycle. Most of thickly populated cities and towns that existed centuries ago are reduced to ruins and give a deserted look now. Cities and towns that were destroyed by natural calamities or razed to the ground by invaders long ago have again been populated thickly and become great trading centres and tourist places. Some of them afford breath-taking scenes and wonderful places ever seen on the earth. Small towns have been developed to be big cities and deserted places have become worth-seeing places. This all happens because change is a constant course of life.
It is but natural that man is attracted by innovations, discoveries, inventions, new creations and change in his life. That is why he has created wonderful things for his ease and comfort. Wonderful, magnificent and sky-high buildings reflect his tendency to high life, luxurious living and glorious and glamorous station of life. Gone are the days when man used to light oil lamp and cooked food by burning firewood and coal. Means of transport, communications and routes of conveyance have drastically changed. Modern inventions have brought wonderful change in our life-style and made our mobility frequent and speedy, and living amazingly convenient.
Some drastic and violent changes were brought about by cruel and wicked invaders who not only plundered wealth and precious things, but also put tens of thousands of innocent people to sword. Genghis khan and Hulagu Khan of Mongol stock are the worst examples of tyranny, scourge, mass killing of Muslims and hostility and ill-will towards Islam. They laid cities, crops and bazaars waste and set libraries and properties of Muslims on fire and reduced magnificent buildings to debris and dust and burnt thousands of precios and rare books to ashes. Their invasions came as wrath of God to teach transgressors a lesson.