The best way is to reach is by train as the major railway station is in the heart of the city. Allahabad lies on the main broad gauge trunk line between Delhi and Calcutta, you have the option for direct trains from Delhi, Kolkata, Mumbai, Chennai, Bangalore and many other cities.
Bamrauli airport is the domestic airport of Allahabad which is just 15km away from the city. You can rent cars through travel agents and enjoy the city around. Airport is well-connected to metros like Delhi, Kolkata and Lucknow.
The city is extremely well connected all across India, you can easily drive through. The roads are reasonably good and well maintained. Buses terminate at the Leader Road bus stand linking Allahabad to almost all the major cities including Delhi (643 kms), Gwalior, Kanpur, Lucknow (204 kms), Meerut and Varanasi (122 kms).