The only reason I can think of why this site features on India's T List, is to give Cochin/Kochi a WHS. Not that Cochin needs to attract even more foreign visitors - I found it a tourist trap completely geared to western tastes. Fortunately I don't think it has any chance of getting in.
Matancherry Palace, locally known as 'Dutch Palace' because they restored it, was built ca. 1555 by the Portuguese. It is located in the south of Fort Cochin peninsular, close to the Jewish town. I rented a bike to get there from the central northern area, a bargain at 50 rupees (0,90 EUR) for a half day. Cycling also has the advantage that you are redeemed of the rickshaw drivers calling out to you every single second. And other tourists either admire or envy you!
The 'palace' is a two tiered white-yellowish, quadrangular building. There's a 5 rupee entrance fee and it gets pretty busy with visitors. I wrote 'palace' because it looks more like a fortress, quite austere with wooden ceilings. Its T List nomination is not clear what the specific reason would be why this should become a WHS, but I guess it's because of the murals. About half of the rooms are adorned with paintings that are sometimes faded, sometimes pretty well-preserved (however in a strange orange colour). They depict scenes of the Ramayana and various Hindu deities. Worth a visit if you're in the area, but not more than that.