The Registan square, reportedly the age old intersection of the trade roads, is the reason why people come to Samarkand. And with good reason. It is one of the most beautiful examples of Islamic architecture you will ever see, right up there with the Alhambra in Spain and the Blue Mosque in Istanbul.
But there are a lot more monuments in Samarakand and around it. Although the old center has not really survived into modern times, you can find reminders of the greatness of the rulers of Samarkand, especially Ulughbek and Tamerlane, all over town. If one wants to enjoy Central Asian nightlife, Samarkand is the place to do it. The city offers most of the options of Tashkent, but at prices that will make one feel like one is still enjoying the budget of Central Asia.