Tus lies 25 km north of Mashhad and was, for centuries, the great city of this corner of Khorasan — the regional capital that Mashhad eventually eclipsed. It was one of the foremost centres of the Persian world until Tamerlane's forces destroyed it in 1389, and the modern village beside the ruins is a quiet heir to that history rather than a continuation of it.
The site is dominated by the remnants of an enormous earthen citadel wall — the Arg of Tus — encircling a flat plateau where the medieval city once stood. Standing on the rampart you get a real sense of the scale of what was lost. The principal monument today is the mausoleum of Ferdowsi, the poet who composed the Shahnameh, Iran's national epic; the grand 20th-century tomb sits in a formal garden and draws a steady stream of Iranian visitors who come as much in literary pilgrimage as in tourism. Nearby stands the more modest domed tomb of the great theologian al-Ghazali, and the Haruniyeh, a striking medieval brick building of uncertain original purpose.
The drive out from Mashhad passes pistachio orchards and farming villages, and the trip pairs naturally with the literary theme — many travellers combine Tus with a visit to Neyshabur, the birthplace and resting place of Omar Khayyam, to make a full day of Khorasan's poets. Tus itself is a half-day at most: an easy taxi ride from the city, with a teahouse or two near the Ferdowsi garden for a pause before the return.