Budhaneelkantha, Kathmandu, Nepal

Approximately half an hour drive from Kathmandu at the foothills of Shivpuri lies the relaxed form of Vishnu called the Budhaneelkanth (बूढ़ानीलकण्ठ)

Lord Vishnu at entrance

main door to the temple complex

Here, old does not reflect to the chronological age but refers to ancient. How and when did the idol come here is not clearly known.
It was built during the seventh or eighth century during the reign of Vishnugupt of Licchavi period. It was brought and located here.
There is another famous legend which mentions that a farmer while tilling his land accidentally struck the deity. Blood started coming out from the ground. The idol was then relocated to its present location.

The moment you set your eyes on the deity, a sense of peace fills you. A five meter Vishnu reclines cross legged peacefully on the coils of the King of serpents, Shesh Naag (शेषनाग ), in a thirteen meter water body. Sheshnaag's 11 hoods form a canopy over Vishnu's head.
He is also referred as Jalakshayana (जलक्षयन ), jal water and shayana sleeping. So, Vishnu sleeping in anantsagar (अनन्तसागर  ) or the cosmic ocean.

close up of reclining Lord Vishnu with silver crown

The name Budhaneelkantha has no association with Buddha. Let me dissect the word and tell you the meanings. Budha (बूढ़ा) means ancient and neelkantha (नीलकण्ठ ) means "blue throat". So it comes out to be "ancient blue throat".

However, "Blue throat" god refers to Lord Shiva. According to the legend, during the cosmic churning of ocean, many things came out along with nectar of gods and poison. Everyone wanted to have the nectar but no one wanted to have the poison. Lord Shiva obliged by drinking that poison. As soon as the poison touched his throat it started burning.

With burning throat, Shiva went to the north of Kathmandu and struck his trident on the ground. As soon as the trident hit the ground, water started coming out. Shiva drank the water to calm the burning. The lake came to be known as Gosaikund. The water in this pond is said to be the water of Gosaikund.

On the right side, Lord Vishnu holds Sudarshan Chakra and a lotus.

On the other side mace and conch can be seen.

Lord Vishnu's feet

Everyone can see from above but only Hindus are permitted to go down to touch the deity's feet. King Pratap Malla, one of the famous rulers of Kathmandu had a prophetic vision. According to it, death would come to any King immediately after he visits this temple.

All successors to the throne refrained from paying homage at this temple. However, it is said that King Birendra Bir Bikram Shah Dev defied this convention and paid a visit to this temple. He and his entire family were soon assasinated, thus ending his lineage. Thanks to Mr. Kumar who updated me on this incident.
A replica of this temple also exists in the Royal Palace which is not open to public viewing. Another sleeping Vishnu resides at Balaju Gardens, in Kathmandu.

Lord Ganesha temple

Shivalinga and yoni just outside Ganesha temple

On the side sits Nandi facing a golden entrance door to Vishnu's temple.

Lord Vishnu on the side of main entrance door

Nandi sitting outside, facing the entrance to Lord Vishnu's door.

Nandi is the mount and devotee of Lord Shiva and this is a Vishnu temple!

It is of course known that Lord Vishnu was worshipped in the 6th and 7th century but then Shaivism took over till the 12th and 13th century.  Vaishnavism was revived during the rule of King Jayasthi Malla in the 14th century.
Was the idol of deity lost during the brief period and later found in a field?

Lord Vishnu rests on Sheshnaag whereas Naag encircles Lord Shiva's neck. Some Shaivites claim that they see a replica of Shiva under Vishnu. Is there a meshing of the two forms?

According to the holy scripture, Ramayana, the major temple at Rameshwaram has been dedicated to Shiva by Lord Ram who was the incarnation of Vishnu.

Even, Tulsi Ramayana is said to have been narrated by Lord Shiva to his consort Parvati.
In that context, do we really find any difference between Lord Shiva and Lord Vishnu? The debate can be unending, but for me I am happy to pay obeisance to both in the same way.