Budget accommodation
Hostels with private rooms, guesthouses, small family hotels and apartments one metro stop outside the centre. The main trap is choosing a cheap room that costs you two taxi rides a day. Look at the transport line before the nightly rate, and read the three star reviews rather than the five star ones, they are usually more accurate about noise and beds.
Lisbon: Arroios. Bangkok: Ari. Barcelona: Poble Sec.